#0183 Build

[ijedouglas]

Cool and you are welcome

After you burn the amp in with the EH's look at hunting down a Quad of Winged C's. Just loaded up a quad in my Music Man. A nice improvement over the JJ's/ EH's (same tube really) IMO

T

Thanks Tony. I ordered a quad of the old production Winged C's and will report back as soon as I have them installed.

Ian

[talbany]

Cool and you are welcome

After you burn the amp in with the EH's look at hunting down a Quad of Winged C's. Just loaded up a quad in my Music Man. A nice improvement over the JJ's/ EH's (same tube really) IMO

T

Thanks Tony. I ordered a quad of the old production Winged C's and will report back as soon as I have them installed.

Ian

Lookin forward to it!

T

[ijedouglas]

Cool and you are welcome

After you burn the amp in with the EH's look at hunting down a Quad of Winged C's. Just loaded up a quad in my Music Man. A nice improvement over the JJ's/ EH's (same tube really) IMO

T

Thanks Tony. I ordered a quad of the old production Winged C's and will report back as soon as I have them installed.

Ian

Lookin forward to it!

T

New tubes installed and they definitely sound a lot smoother. I'll put some hours on them but so far I really like them.

I did run into something strange though, after firing it up and setting the bias, there was a motorboating sound coming from the speakers. I played around for a while and it seemed to quieten down but not totally disappear. I put back the old tubes and it was still there...so not a bum tube. I put the new ones back in, biased and then noticed that when i reached over the power supply board the motorboating went silent (I guess my arm was shielding the open chassis, although it didnt do it before today). I installed some aluminium flashing in the cab and its back to dead silent. I suspect it may be a cap in the power supply, thoughts on what it could be?

Ian

[67plexi]

Look close at 220k V-1 and 68k V-2

[Charlie Wilson]

Thanks Tony. I ordered a quad of the old production Winged C's and will report back as soon as I have them installed.

Ian

Lookin forward to it!

T

New tubes installed and they definitely sound a lot smoother. I'll put some hours on them but so far I really like them.

I did run into something strange though, after firing it up and setting the bias, there was a motorboating sound coming from the speakers. I played around for a while and it seemed to quieten down but not totally disappear. I put back the old tubes and it was still there...so not a bum tube. I put the new ones back in, biased and then noticed that when i reached over the power supply board the motorboating went silent (I guess my arm was shielding the open chassis, although it didnt do it before today). I installed some aluminium flashing in the cab and its back to dead silent. I suspect it may be a cap in the power supply, thoughts on what it could be?

Ian

Ian, I don't think shielding would make a bad cap stop motorboating. Most times I hear people having an issue like that it ends up being a grounding issue but with your amp it seems like it is picking up something externally.
CW

[ijedouglas]

Lookin forward to it!

T

New tubes installed and they definitely sound a lot smoother. I'll put some hours on them but so far I really like them.

I did run into something strange though, after firing it up and setting the bias, there was a motorboating sound coming from the speakers. I played around for a while and it seemed to quieten down but not totally disappear. I put back the old tubes and it was still there...so not a bum tube. I put the new ones back in, biased and then noticed that when i reached over the power supply board the motorboating went silent (I guess my arm was shielding the open chassis, although it didnt do it before today). I installed some aluminium flashing in the cab and its back to dead silent. I suspect it may be a cap in the power supply, thoughts on what it could be?

Ian

Ian, I don't think shielding would make a bad cap stop motorboating. Most times I hear people having an issue like that it ends up being a grounding issue but with your amp it seems like it is picking up something externally.
CW

Thanks Charlie,

Its been running for 2 hours with no more issues.Just strange that it started picking up interference through the power supply. I have been running every eve for around 2-4 hours for a month with no issues. I'll stick with the shielding as its something i was going to do anyway. Thanks for all your help BTW Your Tweedle Dee pics along with advice from Jelle is what got me started

Kind regards

Ian

[ijedouglas]

Look close at 220k V-1 and 68k V-2

Is there something I'm missing? So far the shielding has addressed the issue but if you see there is something there I'll take a closer look

[talbany]

Lookin forward to it!

T

New tubes installed and they definitely sound a lot smoother. I'll put some hours on them but so far I really like them.

I did run into something strange though, after firing it up and setting the bias, there was a motorboating sound coming from the speakers. I played around for a while and it seemed to quieten down but not totally disappear. I put back the old tubes and it was still there...so not a bum tube. I put the new ones back in, biased and then noticed that when i reached over the power supply board the motorboating went silent (I guess my arm was shielding the open chassis, although it didnt do it before today). I installed some aluminium flashing in the cab and its back to dead silent. I suspect it may be a cap in the power supply, thoughts on what it could be?

Ian

Ian, I don't think shielding would make a bad cap stop motorboating. Most times I hear people having an issue like that it ends up being a grounding issue but with your amp it seems like it is picking up something externally.
CW

Hey Ian

I am with Charlie. . If it were me I would want to know what is causing the amp to oscillate.(Especially if it's in my power supply ) My gut tells me it is a bad cap but this is just an educated guess. Let me know if I can help further. You can PM me if you like. BTW did you measure or ohm out the filter caps before you installed them?
Yeah those are sweet tubes glad you like em. The harder you drive them the smoother they get.

Tony

[Charlie Wilson]

Ian, Tony has way more experienced guts than I do but I would like to add that it could be a bad filter cap or a bad connection either ground or hot side of the cap. I also agree that you may want to find out what the problem is before you move on. A oscillation could range from making your amp not sound as good as it could to making your output transformer working way harder than it should. Also, try not to fixate on what you think it may be, we have decided that it is in the power supply but are we sure? What I would do is take your amp out of the head shell and try to get it to do the problem. Then start pulling preamp tubes starting with the V1 then V2 and so on. If it goes away by pulling a preamp tube then it is not a power supply issue(probably). If you can narrow it down to a particular area of the amp it makes it much easier. Other things you could do are get it to do the problem and start (with a chopstick) moving wires around(gently) to see if it changes anything. Also with your chopstick, push on every solder connection while the amp is on you will know if there is a bad one. You did a great job with your amp by the way but I did want to mention your solder connections. You want each eyelet to be a nice even shinny puddle that evenly coats all the wires and leads going in it and I see some in the photos you may want to revisit. What I do after I solder is look at each one with a magnifying glass and make sure they all look good. These amps seem to be real sensitive to less than solid contacts. I also read somewhere that flux in solder is not conductive unless it gets burn and then it can be hydroscopic(absorb water). After I am done soldering I have a large box of Q-Tips and Isopropyl alcohol(not rubbing alcohol!) and I clean each solder joint until it is shiny. Also around the solder joint on the board until no residue is on my Q-Tip. Know that Isopropyl alcohol is very flammable so don't do any resoldering until you know it is dry. Finally, I have taken a few real Dumble amps out of the headshells(or cabinets) and don't recall any with shielding. The shielding may cut down on noise at a gig or whatever but it should not be needed for your amp to function properly. Oh yeah, if you used that aluminum adhesive tape stuff for dryer vents you need to put staples where one strip crosses the other. The adhesive is an insulator. I just noticed that you live about 15 min. away from me.
Hope this helps.
CW

[ijedouglas]

Ian, Tony has way more experienced guts than I do but I would like to add that it could be a bad filter cap or a bad connection either ground or hot side of the cap. I also agree that you may want to find out what the problem is before you move on. A oscillation could range from making your amp not sound as good as it could to making your output transformer working way harder than it should. Also, try not to fixate on what you think it may be, we have decided that it is in the power supply but are we sure? What I would do is take your amp out of the head shell and try to get it to do the problem. Then start pulling preamp tubes starting with the V1 then V2 and so on. If it goes away by pulling a preamp tube then it is not a power supply issue(probably). If you can narrow it down to a particular area of the amp it makes it much easier. Other things you could do are get it to do the problem and start (with a chopstick) moving wires around(gently) to see if it changes anything. Also with your chopstick, push on every solder connection while the amp is on you will know if there is a bad one. You did a great job with your amp by the way but I did want to mention your solder connections. You want each eyelet to be a nice even shinny puddle that evenly coats all the wires and leads going in it and I see some in the photos you may want to revisit. What I do after I solder is look at each one with a magnifying glass and make sure they all look good. These amps seem to be real sensitive to less than solid contacts. I also read somewhere that flux in solder is not conductive unless it gets burn and then it can be hydroscopic(absorb water). After I am done soldering I have a large box of Q-Tips and Isopropyl alcohol(not rubbing alcohol!) and I clean each solder joint until it is shiny. Also around the solder joint on the board until no residue is on my Q-Tip. Know that Isopropyl alcohol is very flammable so don't do any resoldering until you know it is dry. Finally, I have taken a few real Dumble amps out of the headshells(or cabinets) and don't recall any with shielding. The shielding may cut down on noise at a gig or whatever but it should not be needed for your amp to function properly. Oh yeah, if you used that aluminum adhesive tape stuff for dryer vents you need to put staples where one strip crosses the other. The adhesive is an insulator.
Hope this helps.
CW

Thanks Charlie, I really appreciate the help. I'll step through your troubleshooting steps and see what I find. I did a pretty intensive chopstick session last night and nothing came up other than when my hand shielded a very specific part of the power supply board the noise disappeared. Funny thing, I normally clean the flux but I changed so many parts on this build I got sloppy. I'll be cleaning it all up tonight

Ian

[67plexi]

V-2 cold solder joint V-1 220k to ground

183 0.jpg

[ijedouglas]

V-2 cold solder joint V-1 220k to ground

183 0.jpg

Thanks. I'll reflow tonight

[Charlie Wilson]

Good eyes Plexi ! Yeah get rid of that little solder trail to ground on 220k. You want to heat the top of the strip and have it cover the leads of the resistor but not run all the way down. I also find that sometimes I need to ruff up those terminal strips with fine sandpaper to get the solder to hold better.
CW

[ijedouglas]

Problem solved.

Turns out there was a stray lead clipping wedged at the PI trimmer. When I swapped tubes, it must have moved into a position that was causing an arc to ground. When I installed the flashing, it must have moved causing me to think the flashing fixed it I found this while cleaning all the solder joints. Plexi, I checked the joints on V1 and V2, they were solid and the lead to ground was just from the camera angle but I cleaned it up anyway and re-flowed the joint for good measure (great eyes BTW)... V2 has the lead wrapped so the loop makes it look bad but it has a solid physical connection. All the board joints look solid after cleaning. I'll post a pic in a few.

Big thanks to Tony, Charlie and Plexi for your help and support.

Ian

[talbany]

Ian

Great!! Glad it was not a bad cap. I've had internal shorts in caps act the same way! Yours was obviously external

Btw. How does the amp compare side by side with the 183?
Close not so close??

Tony