Hi Guys,
Hello to you all,first post here so be patient please,
I just picked up an old Gibson Skylark 1960 ga-5.The one with blond Tolex and brown grill cloth.
I got it at a car boot sale as non-working.I've had it looked over by a friend who tells me the filter cap is missing other than that its good to go.
He reckons he can find me one if I get him a pic that shows how it was mounted to the chasis and the dimensions of the cap(dia and length).
I found a schematic that tells me it was a 10/10/20uf can type,anybody out there have the same era amp and can show me a pic and tell me how it was mounted and the dimensions???
Thanks in advance for any help,Bigbear.
Gibson Skylark(GA-5) 1960 filter cap.
Moderators: pompeiisneaks, Colossal
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marcoloco961
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Re: Gibson Skylark(GA-5) 1960 filter cap.
I googled that model and came up with one pic. The can cap is the silver cylinder facing down on the right side of the chassis. Hope this helps.
Most can caps mount like this through a hole in the chassis. They look almost like another tube sticking through. The cans ground is the outside casing and it must be well grounded to the chassis. Some cans have ears that fit trough a slot in the chassis and are then twisted, then soldered, while the newer cans usually have a mounting bracket of some sort that needs to be attached to the chassis. Good luck with your project, let us know how it turns out.
Most can caps mount like this through a hole in the chassis. They look almost like another tube sticking through. The cans ground is the outside casing and it must be well grounded to the chassis. Some cans have ears that fit trough a slot in the chassis and are then twisted, then soldered, while the newer cans usually have a mounting bracket of some sort that needs to be attached to the chassis. Good luck with your project, let us know how it turns out.
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marcoloco961
- Posts: 356
- Joined: Wed Feb 25, 2009 3:07 pm
- Location: Colona, Il. U.S.
Re: Gibson Skylark(GA-5) 1960 filter cap.
Here is another pic of an old Silvertone from that era with a can. This one measures 1" dia. and 3" in length. The new one might not be exactly the same as the old, but you can probably make it work either way.
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Re: Gibson Skylark(GA-5) 1960 filter cap.
Please confirm what you've got. The GA5 pic posted above is the "Crestline" GA-5. You say you've got a 1960 Tweed, which is an altogether different amp. The tweed was made from '54-'61, has one 12ZX7, one 6V6 and one 5Y3, and one 8" speaker. Is that what you have?
Here is the schematic for the tweed GA5. It shows 3 filter caps. Any generic 450V rated caps will do. There are two 10u and one 20u. When you open it up, you'll know if you want to use radial or axial caps. If you see the original brown paper caps, these are well past their useful life and IMO, it is ill advised to leave them there. They really do have to be changed.
Great find!
Here is the schematic for the tweed GA5. It shows 3 filter caps. Any generic 450V rated caps will do. There are two 10u and one 20u. When you open it up, you'll know if you want to use radial or axial caps. If you see the original brown paper caps, these are well past their useful life and IMO, it is ill advised to leave them there. They really do have to be changed.
Great find!
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Re: Gibson Skylark(GA-5) 1960 filter cap.
Thanks for your comments guys,
The amp is indeed an earlier blond tolex model 1960,6v6,5y3,12ax7,as you say.Ive uploaded a couple of pics of the chassis.
I can't see where the filter caps(s) may have been attached to the chassis the only hole I see is where the OT is at the rear(in the pic the hole is right above).
This looks no bigger than the hole with the rubber gromet to the left.
In one of the pics you can see a paper strap that comes from the mains cable hole and wraps around the chassis....could the filter cap been held onto the chassis by this????
Thanks again,Bigbear.
The amp is indeed an earlier blond tolex model 1960,6v6,5y3,12ax7,as you say.Ive uploaded a couple of pics of the chassis.
I can't see where the filter caps(s) may have been attached to the chassis the only hole I see is where the OT is at the rear(in the pic the hole is right above).
This looks no bigger than the hole with the rubber gromet to the left.
In one of the pics you can see a paper strap that comes from the mains cable hole and wraps around the chassis....could the filter cap been held onto the chassis by this????
Thanks again,Bigbear.
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Re: Gibson Skylark(GA-5) 1960 filter cap.
How much electronics experience have you got? There are aspects of this work that are quite dangerous and potentially deadly. Caps in particular can be rather nasty, continuing to pack a lethal charge even after the amp has been powered off and unplugged. If you are not up to this, take it to a tech. Any self-respecting electronics repair technician can install the correct caps as long as he's got the schematic.
If you like, and you are feel that you've got the experience to do the work yourself, I'll try to guide you from afar. You must have soldering experience (know how to make a proper joint) and understand basic electronic device safety.
This is not one of those amps that will lend itself well to on the job training. Because this amp is built old school point-to-point, it is quite likely that the caps were simply tied directly to the tube sockets. If you can locate R10 and R12, the caps go at either end of those and in the middle. I can see them -- they aren't hard to find.
Also, please post a picture showing the whole chassis. There may be other safety considerations for this amp.
If you like, and you are feel that you've got the experience to do the work yourself, I'll try to guide you from afar. You must have soldering experience (know how to make a proper joint) and understand basic electronic device safety.
This is not one of those amps that will lend itself well to on the job training. Because this amp is built old school point-to-point, it is quite likely that the caps were simply tied directly to the tube sockets. If you can locate R10 and R12, the caps go at either end of those and in the middle. I can see them -- they aren't hard to find.
Also, please post a picture showing the whole chassis. There may be other safety considerations for this amp.
Re: Gibson Skylark(GA-5) 1960 filter cap.
Hi Phil,
And many thanks for your comments and offer to help me get this thing going.
I have had enough experience to do this......got a multimeter,can discharge caps,solderings not too bad,have replaced bits and pieces through the years.
My only concern with soldering directly to the sockets is that they are quite weak and most wobble/loose,can these type of pins be retensioned?
I'm thinking it may be better to use the extension leads that are in place already and maybe just cable tie or glue the new caps to the chasiss????
Any pros or cons either way??
Also do I have to stick strictly to the cap values?
Finally,if I was to solder to the tube pins where is the best place to solder the negative ends of the caps???
Many Thanks for your time,Bigbear.
P.S. Let me know if there is a particular part of the chasiss you'd like to see and I'll post a pic.
And many thanks for your comments and offer to help me get this thing going.
I have had enough experience to do this......got a multimeter,can discharge caps,solderings not too bad,have replaced bits and pieces through the years.
My only concern with soldering directly to the sockets is that they are quite weak and most wobble/loose,can these type of pins be retensioned?
I'm thinking it may be better to use the extension leads that are in place already and maybe just cable tie or glue the new caps to the chasiss????
Any pros or cons either way??
Also do I have to stick strictly to the cap values?
Finally,if I was to solder to the tube pins where is the best place to solder the negative ends of the caps???
Many Thanks for your time,Bigbear.
P.S. Let me know if there is a particular part of the chasiss you'd like to see and I'll post a pic.
Re: Gibson Skylark(GA-5) 1960 filter cap.
The socket pin holders will feel loose until a tube is inserted.
It's a good idea to stick a junk tube in the socket while soldering to the pins.
Sometimes a bit of solder will leak down into the pin and make inserting a tube hard if not impossible.
It's a good idea to stick a junk tube in the socket while soldering to the pins.
Sometimes a bit of solder will leak down into the pin and make inserting a tube hard if not impossible.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Gibson Skylark(GA-5) 1960 filter cap.
Hello Bigbear,
I'm guessing by the time of your reply and word usage ("boot sale") we are on opposite sides of the pond? The reason I ask is your parts availability and cost may be very different. In the USA, what we need is cheap, easy to find, and comes in a day or 3. I work from my own frame of reference, so let me know if there is a delay finding parts.
Unless tubes are loose in the sockets, I would avoid retensioning. Let me know if you want a pointer on this.
Well, let's see. First you've got to locate the two dropping resistors in the power supply ladder. The large 10K and 22K resistors are on the rectifier socket. It's such a rat's nest there, I can't see which pin numbers. That is where the 5Y3 goes. The 5Y3 uses pins 2 and 8 for the filament supply and pins 4 and 6 for the high voltage supply from the transformer. The rest are used as tie points, like a terminal strip. So, to avoid replacing the tube socket, you'll need to do what you can to keep pins 2, 8, 4, and 6 in good order. If the other pins should break, we'll find a work around.
On the power tube socket (6V6) we are interested in pin 3 (plate or anode) and pin 4 (g2 or screen). Pin 3 connects to the output transformer - just leave that alone, but you need to find the other end of the output transformer to connect to C9, see more below. Pin 4 will connect to the junction of R12 and C6.
Finally, you will need to find the pair of 220K plate load resistors that connect to pins 1 and 6 (plates) of the 12AX7. They will be or should be joined at the end away from the tube socket, where C5 appears on the schematic. You may have to follow the wires.
The 20uf cap goes into the end of the R12 (10K resistor) that is connected to the power supply. The power supply will come from either pin 2 or pin 8 of the rectifier (same as the filament pin), but not both. For brevity, I'll assume pin 2. Substitute pin 8 if I'm wrong. With this being a true PTP build, look for one end of R12 to be directly on pin 2. Pin 2 is where you connect the + side of C9 (20uf). There will also be a connection to one side of the output transformer, without which, there is no music or power supply to the power tube plate.
Now you can see where R12 and R10 meet. That junction is where you attach the + side of C6 (10uf).
Finally, the other end of R20 (22k) should meet R8 and R4 (both 220K). The third filter cap goes to the place where R20, R8 and R4 meet.
OK, so now you are clear where the + side of each filter cap goes? So far, so good. You may find that you can heat the existing solder, add just a little bit to get it wet, and insert the lead from the cap. Since these caps are located close to the 5Y3 socket, you will be able to join all the - side leads together. See if you can hang a terminal strip to stabilize the ground side. I see a bolt sticking up between the red and yellow wires -- see if you can mount a terminal strip on that and also make that your ground point. Since I'm not there, I don't have a clear sense of what else one might do. If there is a great deal of excess solder present, you may want to employ solder braid or a solder sucker to remove some.
Another thought, if the leads on the caps are long enough, is to put a solder friendly ground lug under a ground screw and then you will be good to solder to that lug. This might be preferable. You'll have to decide after you have the caps and do a bit of layout work. You may find you need both a terminal strip and a ground lug.
This is a simple amp. I've broken some layout rules for noise control with the grounds. I don't believe this will create a noise problem. If it does, we'll work on that, but first you need to do something to make the amp functional.
There are two other things that, in my view, are essential to do. One is to change the brown paper cap, which should be C1, the cathode bypass cap on the V1. That one is so old, we don't want to risk it spewing its guts inside the chassis. That one is 20uf, 25 or 50V rating is appropriate there.
BTW, just get close with the cap values. 8, 10, 20, 22, 25 are all common values. 8 will work for 10. 22 and 25 will work for 20. You can use three 20uf filter caps instead of two 10uf and one 20uf. Those old amps had caps rated +/- 50%, I think.
Finally, and actually a very important safety mod, you must clip the death cap and replace the two prong non polarized cord with a proper 3 wire cord. The death cap is that bumble bee cap you see over the rectifier socket. These are valuable caps, so remove it to preserve lead length if you can. Then find a suitable 3 wire cord to supply the primary side of the power transformer.
I don't know in what country you are located. You may have issues with my instructions on wiring the primary due to differences. In the USA, we have single phase 120VAC. I don't know what you have and what is required where you are. In the USA, we wire the + side of the line feed to the fuse and then to the swtich. The other side of the switch connects to either of the primary leads on the transformer. The - or neutral feed from the line supply is connected directly to the transformer.. The redundant ground is connected to a dedicated bolt (no other grounds here) that runs through the chassis near where the wire enters. You may need to drill a hole and install a bolt. Use a ring lug (not an open "U" lug) on the redundant ground wire, and make it with enough service slack so that when something goes wrong and the power cord is being pulled from the chassis unknowingly, the ground will be the last to break.
You may need to use a double pole switch to break both the line and neutral supply from the wall. This is really a very good practice and required in many European countries and I believe down under, as well.
I shouldn't assume...you must always have a speaker load connected to the output transformer when power is on, otherwise the output transformer will blow.
Have you got any way of confirming this amp is meant for your wall voltage (if not 120VAC)? This point worries me. If you apply 220 to a 110 (from the old days) transformer, the result will not be pretty.
Find on the internet the dim bulb tester and make one. This is essential for your first power up. If you have a short, the bulb goes bright and saves your amp. Think of it as very cheap insurance.
You mention using existing leads instead of disturbing what's there. Certainly, this is OK. You may want to install a pair of terminal strips about 2" apart. You can hang the three filter caps between them and run wire to the appropriate locations or bring existing wire to the terminal strips. I didn't cover this above because there are already lots of words and I was trying to be very clear. You'll be the judge of what alternatives work for this amp.
OK, you've got your work cut out for you, don't you? Anything not clear? Please ask.
Finally, the disclaimer...I have no formal electronics training. This is a hobby for me. You do this work at your own risk and peril. So, please be careful.
Phil
I'm guessing by the time of your reply and word usage ("boot sale") we are on opposite sides of the pond? The reason I ask is your parts availability and cost may be very different. In the USA, what we need is cheap, easy to find, and comes in a day or 3. I work from my own frame of reference, so let me know if there is a delay finding parts.
Unless tubes are loose in the sockets, I would avoid retensioning. Let me know if you want a pointer on this.
Well, let's see. First you've got to locate the two dropping resistors in the power supply ladder. The large 10K and 22K resistors are on the rectifier socket. It's such a rat's nest there, I can't see which pin numbers. That is where the 5Y3 goes. The 5Y3 uses pins 2 and 8 for the filament supply and pins 4 and 6 for the high voltage supply from the transformer. The rest are used as tie points, like a terminal strip. So, to avoid replacing the tube socket, you'll need to do what you can to keep pins 2, 8, 4, and 6 in good order. If the other pins should break, we'll find a work around.
On the power tube socket (6V6) we are interested in pin 3 (plate or anode) and pin 4 (g2 or screen). Pin 3 connects to the output transformer - just leave that alone, but you need to find the other end of the output transformer to connect to C9, see more below. Pin 4 will connect to the junction of R12 and C6.
Finally, you will need to find the pair of 220K plate load resistors that connect to pins 1 and 6 (plates) of the 12AX7. They will be or should be joined at the end away from the tube socket, where C5 appears on the schematic. You may have to follow the wires.
The 20uf cap goes into the end of the R12 (10K resistor) that is connected to the power supply. The power supply will come from either pin 2 or pin 8 of the rectifier (same as the filament pin), but not both. For brevity, I'll assume pin 2. Substitute pin 8 if I'm wrong. With this being a true PTP build, look for one end of R12 to be directly on pin 2. Pin 2 is where you connect the + side of C9 (20uf). There will also be a connection to one side of the output transformer, without which, there is no music or power supply to the power tube plate.
Now you can see where R12 and R10 meet. That junction is where you attach the + side of C6 (10uf).
Finally, the other end of R20 (22k) should meet R8 and R4 (both 220K). The third filter cap goes to the place where R20, R8 and R4 meet.
OK, so now you are clear where the + side of each filter cap goes? So far, so good. You may find that you can heat the existing solder, add just a little bit to get it wet, and insert the lead from the cap. Since these caps are located close to the 5Y3 socket, you will be able to join all the - side leads together. See if you can hang a terminal strip to stabilize the ground side. I see a bolt sticking up between the red and yellow wires -- see if you can mount a terminal strip on that and also make that your ground point. Since I'm not there, I don't have a clear sense of what else one might do. If there is a great deal of excess solder present, you may want to employ solder braid or a solder sucker to remove some.
Another thought, if the leads on the caps are long enough, is to put a solder friendly ground lug under a ground screw and then you will be good to solder to that lug. This might be preferable. You'll have to decide after you have the caps and do a bit of layout work. You may find you need both a terminal strip and a ground lug.
This is a simple amp. I've broken some layout rules for noise control with the grounds. I don't believe this will create a noise problem. If it does, we'll work on that, but first you need to do something to make the amp functional.
There are two other things that, in my view, are essential to do. One is to change the brown paper cap, which should be C1, the cathode bypass cap on the V1. That one is so old, we don't want to risk it spewing its guts inside the chassis. That one is 20uf, 25 or 50V rating is appropriate there.
BTW, just get close with the cap values. 8, 10, 20, 22, 25 are all common values. 8 will work for 10. 22 and 25 will work for 20. You can use three 20uf filter caps instead of two 10uf and one 20uf. Those old amps had caps rated +/- 50%, I think.
Finally, and actually a very important safety mod, you must clip the death cap and replace the two prong non polarized cord with a proper 3 wire cord. The death cap is that bumble bee cap you see over the rectifier socket. These are valuable caps, so remove it to preserve lead length if you can. Then find a suitable 3 wire cord to supply the primary side of the power transformer.
I don't know in what country you are located. You may have issues with my instructions on wiring the primary due to differences. In the USA, we have single phase 120VAC. I don't know what you have and what is required where you are. In the USA, we wire the + side of the line feed to the fuse and then to the swtich. The other side of the switch connects to either of the primary leads on the transformer. The - or neutral feed from the line supply is connected directly to the transformer.. The redundant ground is connected to a dedicated bolt (no other grounds here) that runs through the chassis near where the wire enters. You may need to drill a hole and install a bolt. Use a ring lug (not an open "U" lug) on the redundant ground wire, and make it with enough service slack so that when something goes wrong and the power cord is being pulled from the chassis unknowingly, the ground will be the last to break.
You may need to use a double pole switch to break both the line and neutral supply from the wall. This is really a very good practice and required in many European countries and I believe down under, as well.
I shouldn't assume...you must always have a speaker load connected to the output transformer when power is on, otherwise the output transformer will blow.
Have you got any way of confirming this amp is meant for your wall voltage (if not 120VAC)? This point worries me. If you apply 220 to a 110 (from the old days) transformer, the result will not be pretty.
Find on the internet the dim bulb tester and make one. This is essential for your first power up. If you have a short, the bulb goes bright and saves your amp. Think of it as very cheap insurance.
You mention using existing leads instead of disturbing what's there. Certainly, this is OK. You may want to install a pair of terminal strips about 2" apart. You can hang the three filter caps between them and run wire to the appropriate locations or bring existing wire to the terminal strips. I didn't cover this above because there are already lots of words and I was trying to be very clear. You'll be the judge of what alternatives work for this amp.
OK, you've got your work cut out for you, don't you? Anything not clear? Please ask.
Finally, the disclaimer...I have no formal electronics training. This is a hobby for me. You do this work at your own risk and peril. So, please be careful.
Phil
Re: Gibson Skylark(GA-5) 1960 filter cap.
Hi Phil,
Many,many thanks for your lengthy reply.The internet is a great
place when complete strangers are willing to help one another out!
Your right I'm in the U.K.,we run 240v over here so today I got a friend to check out the transformer and he reckons its the 110v original but said it tests OK and looks in good condition.
He reckons it would be fine to use the two prong cable through a isolated step-down transformer but I think I'm gonna change to a three prong cable just to be sure.
Hes also given me some caps to use for the filter caps.They are two 47uf 450v and one 80uf 450v,hes told me not to worry that they are higher than the stated 10/10/20 values,
He reckons the higher values may even reduce hum,the only thing he did say was to be sure the rectifier filter cap got one of the 47uf and not 80uf????not sure why??
Anyhoo,gotta get a few more bits together and I'll try and get this little thing up and running............been thinking of a decent speaker to upgrade this jensen to......any thoughts??
Cheers again,Bigbear.
Many,many thanks for your lengthy reply.The internet is a great
place when complete strangers are willing to help one another out!
Your right I'm in the U.K.,we run 240v over here so today I got a friend to check out the transformer and he reckons its the 110v original but said it tests OK and looks in good condition.
He reckons it would be fine to use the two prong cable through a isolated step-down transformer but I think I'm gonna change to a three prong cable just to be sure.
Hes also given me some caps to use for the filter caps.They are two 47uf 450v and one 80uf 450v,hes told me not to worry that they are higher than the stated 10/10/20 values,
He reckons the higher values may even reduce hum,the only thing he did say was to be sure the rectifier filter cap got one of the 47uf and not 80uf????not sure why??
Anyhoo,gotta get a few more bits together and I'll try and get this little thing up and running............been thinking of a decent speaker to upgrade this jensen to......any thoughts??
Cheers again,Bigbear.
Re: Gibson Skylark(GA-5) 1960 filter cap.
Careful changing the values of the filter caps too much.
Tube rectifiers have a maximum filter cap that can be used.
For the 5Y3 that is 32uF.
Usually you can go above the original by 10-15% with no problem but to keep it the same as it was intended you should try to find the same value.
The voltage rating of the cap must be at least as big as the existing but you can safely use a cap that has a higher voltage rating and many times it is desirable to do that.
Because the wall voltages are higher than they were when these amps were made, the secondary voltages go higher due to that.
New electrolytic capacitors are much smaller than they used to be so it's easy to fit the new ones in there.
Your amp only appears to have seven caps, unless I missed one.
Make sure the caps in the power supply are rated for at least 450v.
Tube rectifiers have a maximum filter cap that can be used.
For the 5Y3 that is 32uF.
Usually you can go above the original by 10-15% with no problem but to keep it the same as it was intended you should try to find the same value.
The voltage rating of the cap must be at least as big as the existing but you can safely use a cap that has a higher voltage rating and many times it is desirable to do that.
Because the wall voltages are higher than they were when these amps were made, the secondary voltages go higher due to that.
New electrolytic capacitors are much smaller than they used to be so it's easy to fit the new ones in there.
Your amp only appears to have seven caps, unless I missed one.
Make sure the caps in the power supply are rated for at least 450v.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Gibson Skylark(GA-5) 1960 filter cap.
I love seeing these old amps posted thanks 
Mark
Mark
Re: Gibson Skylark(GA-5) 1960 filter cap.
I'm with Structo/Tom on the cap values. Those will fry the 5Y3 PDQ. You can put the two 47uf in series and that gives you one 23uf. That's good for the main filter, but it will be awkwardly big. I'd reject the 80uf all together. How expensive could caps be in the UK? They are needed in other electronic gear, so they must be available. I can't suggest where to go. There are two places that come to mind, Maplin and Tube Town (somewhere in Germany?). The Maplin website is crap.
I found on the Tube Town website:
http://www.tube-town.net/ttstore/index. ... 7_F-T.html
http://www.tube-town.net/ttstore/index. ... adial.html
http://www.tube-town.net/ttstore/index. ... axial.html
JJ 4 section can cap 40u-20u-20u-20u EUR 11.10, the clamp is extra and you need it. You can modify the clamp by bending the mount so it will hold the cap sideways. I'll try to post a picture. Cap off the 40u with a bit of heat shrink tubing and use the three 20u sections. With a can, you only have one ground to deal with. This may prove to be the most convenient.
There are also JJ singles:
8uf 450v EUR 2.39
22uf 500v EUR 2.95
22u 35V EUR 0.29 -- this is the right one for that brown paper bypass cap that is still there.
The high voltage caps are on the expensive side but not outrageous.
There are less costly F&T caps that should be fine. I would get:
22uf 450V EUR 1.20
10uf 350V EUR 0.82 - I'm a little concerned the voltage rating is too low; I'd opt for the JJ 8uf or go for the F&T 22uf. IMO, you are better off with the 22uf and it won't hurt the amp or the rectifier.
They've also got radial caps that look to be suitable and almost as cheap as dirt, but I think they will not be so easy to work with.
Thank your friend, but I think he has given you a bum steer.
You should be OK with the 2 prong feed if you use a 240:120 step down isolation transformer. If you want to make the change, that is the safe thing to do, so go ahead, but not needed with the iso.
As for the speaker, what's in there now? If unlabled, there should be a 6 digit number on the rim (maybe elsewhere) that will tell us what it is. I'm unsure about a replacement, but I suppose the 8" Jensen will be OK if there's nothing else.
And, for the helping out part, you've got to know that others did this for me. I know how much I appreciated it. It seems like the right thing to do, so the pleasure is all mine. Also, I have an interest in old Gibson amps, so you've hit me at a soft spot.
You'll do fine with this. There's no hurry. Get the right caps.
You also should replace the cathode cap on the power tube (6V6). you'll need a 20uf 25-50V cap there, basically the same thing as you need for V1.
Good luck.
I found on the Tube Town website:
http://www.tube-town.net/ttstore/index. ... 7_F-T.html
http://www.tube-town.net/ttstore/index. ... adial.html
http://www.tube-town.net/ttstore/index. ... axial.html
JJ 4 section can cap 40u-20u-20u-20u EUR 11.10, the clamp is extra and you need it. You can modify the clamp by bending the mount so it will hold the cap sideways. I'll try to post a picture. Cap off the 40u with a bit of heat shrink tubing and use the three 20u sections. With a can, you only have one ground to deal with. This may prove to be the most convenient.
There are also JJ singles:
8uf 450v EUR 2.39
22uf 500v EUR 2.95
22u 35V EUR 0.29 -- this is the right one for that brown paper bypass cap that is still there.
The high voltage caps are on the expensive side but not outrageous.
There are less costly F&T caps that should be fine. I would get:
22uf 450V EUR 1.20
10uf 350V EUR 0.82 - I'm a little concerned the voltage rating is too low; I'd opt for the JJ 8uf or go for the F&T 22uf. IMO, you are better off with the 22uf and it won't hurt the amp or the rectifier.
They've also got radial caps that look to be suitable and almost as cheap as dirt, but I think they will not be so easy to work with.
Thank your friend, but I think he has given you a bum steer.
You should be OK with the 2 prong feed if you use a 240:120 step down isolation transformer. If you want to make the change, that is the safe thing to do, so go ahead, but not needed with the iso.
As for the speaker, what's in there now? If unlabled, there should be a 6 digit number on the rim (maybe elsewhere) that will tell us what it is. I'm unsure about a replacement, but I suppose the 8" Jensen will be OK if there's nothing else.
And, for the helping out part, you've got to know that others did this for me. I know how much I appreciated it. It seems like the right thing to do, so the pleasure is all mine. Also, I have an interest in old Gibson amps, so you've hit me at a soft spot.
You'll do fine with this. There's no hurry. Get the right caps.
You also should replace the cathode cap on the power tube (6V6). you'll need a 20uf 25-50V cap there, basically the same thing as you need for V1.
Good luck.
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Re: Gibson Skylark(GA-5) 1960 filter cap.
Hi Guys,
I'm back.....finally got the parts and time to do a bit of work to this little beast.
Got some RIFA 22uf managed to secure them to the sockets(not an easy job!)there seemed to be the remains of a lug through the chasiss(maybe the original ground lug for the filters??) so I drilled a hole through it and grounded them to it.
Also replaced both the large brown Astron cap and the black sprague cap and managed to keep the leads and save the attached resistors(again not easy!)
Cut the so-called Death Cap and replaced the 2 prong cord for a 3 prong.Used one of the bolts on the PT for a ground.....will this suffice??or should I drill a dedicated hole and use a lug??
Anyhoo the important bit......does she work....you bet your ass it does!!!!
Fired it up and all is well......its got alot of spank for such a little guy....a little darker and a little dirtier than a F Champ.
I have a nice 12" 1960 P12Q that I'm currently building a cab for...can't wait to hear it through this.
One thing though this amp is real quiet except for turning the volume knob there is quite a bit of static/white noise I thought it might be a dirty pot but I swapped it for a known good one and same thing happens.
It happens with or without guitar plugged in and only when turning the knob otherwise its real quiet.
I know its probably a resistor but any ideas which one???
I've included a few more pics.
Any thoughts on the static/white noise most appreciated.
Cheers,Bigbear.
I'm back.....finally got the parts and time to do a bit of work to this little beast.
Got some RIFA 22uf managed to secure them to the sockets(not an easy job!)there seemed to be the remains of a lug through the chasiss(maybe the original ground lug for the filters??) so I drilled a hole through it and grounded them to it.
Also replaced both the large brown Astron cap and the black sprague cap and managed to keep the leads and save the attached resistors(again not easy!)
Cut the so-called Death Cap and replaced the 2 prong cord for a 3 prong.Used one of the bolts on the PT for a ground.....will this suffice??or should I drill a dedicated hole and use a lug??
Anyhoo the important bit......does she work....you bet your ass it does!!!!
Fired it up and all is well......its got alot of spank for such a little guy....a little darker and a little dirtier than a F Champ.
I have a nice 12" 1960 P12Q that I'm currently building a cab for...can't wait to hear it through this.
One thing though this amp is real quiet except for turning the volume knob there is quite a bit of static/white noise I thought it might be a dirty pot but I swapped it for a known good one and same thing happens.
It happens with or without guitar plugged in and only when turning the knob otherwise its real quiet.
I know its probably a resistor but any ideas which one???
I've included a few more pics.
Any thoughts on the static/white noise most appreciated.
Cheers,Bigbear.
You do not have the required permissions to view the files attached to this post.
Re: Gibson Skylark(GA-5) 1960 filter cap.
Looks like I happened to show up at just the right time! I think what you did is good and I'm pleased to hear that it sounds good.
I don't quite know what to make of the scratchy pot if you replaced it and it still isn't right. The only thing that strikes me is that the replacement is also bad? Try some contact cleaner inside the pot, and rotate it back and forth quickly several times. Maybe you just live with this?
The only thing I see that may be a concern is the way you've mounted the filter caps. Since I don't have the actual piece on my bench, I have to go by the picture. It looks to me like they are hanging by the wires with no support. What concerns me is, in a combo amp, there is vibration. If these are moving, you might experience some unanticipated and unwanted noise. At the very least, I might think about running a bit of hot glue between them and then between the lowest one and the chassis deck.
Nice job, really!!!! It is good to see one of these old Gibsons brought back from the brink. Thanks for the nice pictures, too.
I don't quite know what to make of the scratchy pot if you replaced it and it still isn't right. The only thing that strikes me is that the replacement is also bad? Try some contact cleaner inside the pot, and rotate it back and forth quickly several times. Maybe you just live with this?
The only thing I see that may be a concern is the way you've mounted the filter caps. Since I don't have the actual piece on my bench, I have to go by the picture. It looks to me like they are hanging by the wires with no support. What concerns me is, in a combo amp, there is vibration. If these are moving, you might experience some unanticipated and unwanted noise. At the very least, I might think about running a bit of hot glue between them and then between the lowest one and the chassis deck.
Nice job, really!!!! It is good to see one of these old Gibsons brought back from the brink. Thanks for the nice pictures, too.