66-J Issues

Greetings Everyone,

Been researching for a couple weeks now and have decided the safest bet is to ask, rather than assume.

I have a 50's Guild 66-J that I bought off a friend a year or two ago and been loving it. However, about a month ago I have started hearing the occasional noise that has now turned fairly constant and is driving me to no longer use it. Spoke with my friend and he seems to think that it is likely the multi-section can type capacitor and that it should be easy to find a replacement, but thought I should ask the folks here who know this particular type of amp.

Unfortunately, I am now realizing that I cannot directly post a sound clip and pictures as they need to hosted somewhere else??????
I have the brown and tweed with spaghetti swirls 66-J. I would describe the sound like a sizzling buzz. It is on all channels, at all volumes, and nothing but the standby switch effects it. I have tapped all the tubes with a chopstick and got nothing as well.

I know that this is not a lot to go on but I live in the sticks and it is 2 1/2 hours to a city where there would be an amp tech, and even then, I do not know one. I can solder well enough and would be confident enough if I had direction and parts.

Anyone able/willing to share their thoughts? I would be most grateful!

Without seeing/hearing it...
The multi sectional cap should just be replaced with a terminal strip with radial caps. They are smaller, higher quality, and you can see when they are going bad. Leave the cancap in for looks.

Thanks for the reply Default!

I had read about switching over to a terminal strip with radial caps from my research. The fun part will be finding the right parts, knowing which gets soldered to what and the proper placement of the new terminal strip as it is (as you know) pretty tight in there....

Are there preferred parts and a preferred location when doing this?

I took out the chassis and looked at the can style cap and it reads:
111068
40 - 450 DC D laying down
20 - 450 DC Square
10 - 450 DC Triangle
100 - 50 DC
CAN COM NEG
85 C (2)in a circle 303
D12988 417

Not sure what all this means and maybe this is over my ability but if it can be explained in a way that I can fix it, I would be most grateful. However, I understand that you may not want to take the time to deal with a greenhorn over the internet as well. That would be totally understandable.

Appreciate your help!

Still at work, will check back when I get home.

Welcome. You should be able to posts pics without hosting elsewhere. Depending on your device and browser sometimes it is as simple as just "dragging" the picture into the reply. Failing that, there is an Insert Image icon/button that can be used. Sound clips do have to be hosted elsewhere.

As far as the multicap values: The D, square, triangle correspond to the terminals on the capacitor.

111068 I think this is a part number.
40 - 450 DC D laying down 450 volt rating. This section is almost certainly connected to the output of the rectifier tube. (5Y3GT) This value is high for the 5Y3gt. The spec sheet calls for 20 mfd, so you can safely use a 22mfd radial capacitor.
20 - 450 DC Square 450 volt rating. Probably goes to the screens of the 6V6gts. You can replace this with a radial 22mfd, or safely bump this up to a 33mfd.
10 - 450 DC Triangle 450 volt rating. This section goes to the supply to the preamp tubes. You could go with the stock value, or bump this up to 22mfd, which I would do. A little better filtering.
****** On a project 99-J I have, there is a .47mfd capacitor on the preamp end of the power supply. I have no idea what minimal filtering that is supposed to accomplish, but replace this with a 10-22mfd cap*****
100 - 50 DC A 50 volt rating is a dead giveaway that this section is the bypass capacitor for the big (probably green) resistor that biases the 6V6GT output tubes. Replace that with a similar value and rating cap.
CAN COM NEG The outside of this cap is connected to the chassis to complete the filtering circuit.
85 C (2)in a circle 303 Sprague's EIA code is 303, so Sprague made this cap.
D12988 417 417 indicates this cap was made in the 17th week of 1954.

So it's the power supply filter caps doing this?

Most likely. In any case, they need to be replaced. When it comes down to it, though, I would have to see it.

Thank you soo much for taking the time and energy to help me out on this Default....I really do appreciate it.

Do not have time to fully digest it yet so I may still have a couple questions, but from what I read quickly it is pretty clear in my head so far. Will just have to look at the wiring and see if it makes sense there as well. Pretty sure it will once I get to tracing everything.

Not sure if I should ask if there is a preferred vendor or brand for these parts or which ones to avoid but any suggestions would be welcomed that way. I would rather do it right as this ol amp deserves it.

and thanks for the welcome and heads up fronobulax ...I will try to at least get some pictures up when I get some time..

You should take it to a tech, for sure. Where are you located?

I am in south central New Mexico....

Any idea on how much something like this would cost?
Unfortunately, money is pretty tight these days ...

I don't know of anyone in your area, unfortunately. @Darryl Hattenhauer might know somebody closer. He's in Arizona. If you are willing to ship the chassis, Jim Walton is the man in Philadelphia, but there have to be guys closer.

Well...I am not going to hold my breath but I may have it fixed.....I was thinking about it and realized that it got worse after I pulled the chassis and the clamp on the can to look for specs. Which told my brain it could just be a bad solder joint. So last night I pulled the chassis back out and found 3 or 4 suspect solder joints in various places (one on the multi-section can, one on the first preamp socket, one on the ground and another somewhere I cannot remember right now)....Nothing too bad or obvious but this poor boy has to try and do all he can to save money while still having my amp functional. So in the wee hours of the morning, whilst the rest of the world was sleeping, I was out in the shop with my trusty iron heated up dressing some solder joints.

After lunch, I only had time to quickly test it for a few minutes and she is sounding good. There were two main noises, one was the sizzling buzz and that was constant as soon as I hit any note....That seems to be gone.....The other was more like a gurgly break up when I hit any note on the guitar below the C on the 6th string (bass notes) which in my few minute test only shows up on the lowest few notes and is barely present now...(I play clean by the way)

Of course, further scientific research will be conducted during my normal music time in the evening to see if it all holds true with a more thorough test. Sure would be nice to be able to wait until I have some cash and can find someone worthy in my area to take her to. So if anyone knows an amp tech that can be trusted in New Mexico please let me know.

The presumed original Jensen P12R looks like a 1956, Default believed the can to be dated 1954, and I pulled 134745 BA211-1880 off of one of the 500K pots (So that looks to be a 57' Centralab????)

I will report back after I have time to do more testing....In the meantime here are some pictures.

Nice to see it has had the signal caps replaced.
The blue sprague should be secured better.

Also, you really should bypass the can and put new caps in for filtering. This old, you are asking for a dead short to ground.

My experience is that there are no guitar or amp techs in SW New Mexico, or SE Arizona. There may be somebody in Tucson west.
Are you in the Silver City area? If so there might be somebody in Las Cruces or El Paso.

Jardin said:

I pulled 134745 BA211-1880 off of one of the 500K pots (So that looks to be a 57' Centralab?)

Click to expand...

Correct. CentraLab (134), 1957, week 45.
BA211-1880 is the same partnumber like in my '56 Aristocrat M-75.

Those are mine from week 09 in 1956:




And the Jensen speaker is correctly dated as well. 220 =Jensen, 6 =1956, 39 = week 39.




Ralf

After a few hours of playing through her I would say she is feeling better and sounding much better....still a little broken up and gurgly in the low end but not too bad. I guess I will cross that bridge when I can afford to pay the toll.

I did find an amp tech that is and hour and half from me in Las Cruces http://carlscustomamps.com/. So that is probably who I will call to have her properly looked over in the future.

Just a reminder that it is not a fender style tone stack. Twelve o'clock on treble and bass is no tone control. Counterclockwise is cut, clockwise is boost.

Right...that is one of the things I love about these amps. Much better tone control in my opinion/experience (at least better to me).

The Break up / gurgle I am hearing may just be a need for some TLC due to drift or may be a need for some new tubes. Not sure the story on the tubes that are in her so I may just start by replacing them....But then my brain starts nagging and I may decide to take it to the tech first to make sure everything is within spec ...You know chicken or the egg....The fact is money is tight, so it will all have to wait a bit.

Thanks again for all your help!