Need some help with a Gretsch 6150 please

[chordball]

Hi Everyone,

I've been a member here for quite some time but this is my first post. I started off building a D'Lite and have since built a 5E3 and plan on rebuilding the D'Lite now that I have a better understanding of the circuit (and amps in general) thanks to this forum.

Anyway, a co-worker gave me a 1961 Gretsch 6150 to tune up for him and I have a couple of questions. First is about the filter caps. This is a can cap with 20/10/10 uF @ 450 VDC. I've searched everywhere I know and can't find a replacement. Does anyone know of a source? I am not sure if this needs to replaced or not yet, but any info on this would be appreciated. By the way, I have played the amp and it seems to be working good with only a little hum which I suspect is inherent to these amps, but I really have nothing to compare it to.

Next is the volume pot. Right now the pot is seized up, but thankfully in the full on position. My plan is to try to get this one working again, but my hopes are not high. From what I've gathered, this is an on/off pot, similar to the one mojotone sells in their 5f1 kits http://www.mojotone.com/amp-parts/Alpha ... -Tweed-Amp. That would make a great replacement, but the only problem is the Gretsch needs a 500KA instead of a 1MA. Does anyone know of a source for a replacement?

Here is the schematic and a pic of the pot in question. Thanks for taking the time to look!

Chad

[img:767:563]http://img196.imageshack.us/img196/9605 ... 50767w.jpg[/img]

[img:640:480]http://img705.imageshack.us/img705/8123/dscn2163u.jpg[/img]

[img:640:480]http://img541.imageshack.us/img541/4936/dscn2161f.jpg[/img][/url]

[surfsup]

I am curious if you could put a resistor in parallel with a new 1M value replacement pot to lower the overall value to 500k when max?

[billyz]

Spray it with faderlube or lubatrol. Let it soak a bit them spray some more. Gently work it back and forth. I bet it will come free. You can also, gently bend the tabs back and open it up and clean it with fader lube.
be sure to get some lube down the shaft and bushing. let it soak before trying to rotate it.

I have saved almost everyone I have tried to free up.

Those caps are hard to find , I usually disconnect the can and leave it for looks and use axial types.

If the pot is toast a 1m will work fine. no need to use resistors unless you are trying to change the sweep.

[chordball]

Thanks for the tips so far guys.

billyz, where do you get lubatrol? I did a search for it and am not finding much except for a few references regarding cleaning and one post on flickr that says it is hard to find. I think I'll opt for the faderlube but I was just curious. This is the stuff, right? http://store.caig.com/s.nl/sc.2/category.293/.f

[billyz]

Thanks for the tips so far guys.

billyz, where do you get lubatrol? I did a search for it and am not finding much except for a few references regarding cleaning and one post on flickr that says it is hard to find. I think I'll opt for the faderlube but I was just curious. This is the stuff, right? http://store.caig.com/s.nl/sc.2/category.293/.f

yes, that is the stuff. They keep changing the name.

Lubatrol may not be available any more, I don't know, Same thing though. Don't use blue shower on pots it will kill them.

You can find Caig fader whatever at fry's electronic too.

[jjman]

[img:275:500]http://www.tubesandmore.com/cemirror/in ... -10-10.GIF[/img]

http://www.tubesandmore.com/scripts/fox ... 0-10-10-10

Ignore the extra section and check the dimensions.

[cobalt]

hey,

tubesandmore is saying that this item is not in stock right now.
but since they make them, i would hope it will not be long.

weirddave

[KT66]

Those caps are hard to find , I usually disconnect the can and leave it for looks and use axial types.

Another advantage of using axials for this besides the hassle of getting the old one out is that you can better control the grounding scheme. Where the ground connection is made for power supply filters can affect the noise level. Below is a pic of a Vintage Airline amp that I did this to, I grounded the first 2 filters right at the PT CT /power tube cathode and grounded the third one at the point in the preamp section where the preamp cathodes were grounded, and it helped lower the noise floor.

I know your schematic shows otherwise, but Valco amps of this vintage often have the heater filament setup where one leg is grounded and there is no center tap - if this is the case you should change it to the false CT variety by using 2 100 ohm resistors - this will help a lot with the noise.

Another noise reduction trick that might be worth trying is to elevate the heater CT from ground by disconnecting it from the chassis and connecting it to the power tube cathode - I have had success with this in little Valcos like yours.

One thing you really should do for safety is to change the power cord to a 3 prong cord and remove the death cap, I have attached a pic for that below. You don't want your friend to end up like Keith Relf : http://en.wikipedia.org/wiki/Keith_Relf

[chordball]

Thanks for the link to the can cap. I'll check dim's later and see how they compare. If it will fit, I can tackle the other things first while waiting on them to be re-stocked.

KT66,
Believe me, the first thing that came to mind when I saw the amp was "Replace that power cord!" It's the old 2 prong and has had a longer section spliced on to the original cord. I didn't get a chance to look at the heater filament setup last night but I will tonight, although it may be the weekend before I get to work on it. I will follow your advice about the filter caps if I decide the can is not going to work out. Thanks for the diagram - that's very helpful!

Chad

[jmohr58]

Here is another link for High Voltage Caps including multi sectioned cans.
http://www.justradios.com/capacitors.html

[jmohr58]

They do sometimes suggest updating to seperate electrlyic capacitors. Disconnect the original Can and leave it in place for show.