Quote from: J M Fahey on March 12, 2014, 06:07:30 AM...And you already have a killer speaker.

+1 on this.  Those Jensen Mods are a great value.  I recently sold  a peavey amp where the speaker was dead so I replaced it with 12"-70W Jensen mod.  The buyer was playing the amp and made the comment that "These old Eminences are good" and I told him, no, it's a Jensen Mod.  "Huh!", he said.

What pre-amp tube do you have?    Take a look at this and see if anything looks similar to your set-up.

Transistor radios are addictive.  Stop now before you end up with a box full.  :tu:

Bias adjustment - don't fool with it.  See attached.

I bought a Plush 1060 head with a "blown" transformer, that was supposedly diagnosed by a local well-known shop, but turned out was not blown transformer at all. 

Who says the transformer is blown?  The same guy who doesn't know what else is wrong with it?  Did he test it?  How?  If he cant tell you, ask if you can test it yourself, or make a low offer as others suggested.

How do you get the tolex so clean?

I like your photos.  The first head was a bit of deja vu for me, I just worked on a peavey mixer amp xr-400, and the similarity of construction reminded  me of it, it was also about 1979 or so.  I also have a classic vt 212 combo from the same era.  I fixed it to sell, and it works fine, but is really filthy exterior. 

Well I followed the warm soapy water on a rag, then damp tag then alcohol.  I tried to clean all the transistor connections/solder joints. I unbolted ( but not un soldered) the boards, the big filter caps, the pots, and cleaned everywhere I could reach.  I put it back together and I am happy to report it is substantially improved.  I haven't played it long enough yet to know if it has any other issues,  but the bath really has helped.

I am intrigued by the kerosene comments.  I have heard if using naphtha, like lighter fluid to clean guitars.  I guess it is similar to kerosene.

Dr Gonz:  Thanks for the link.  It looks like the first link under "200" is the right one, ignoring the reverb and vibrato boards, which i don't have.

I was halfway through the alcohol when I realized you meant for me to clean with it. 

I just finished wiping it out.  It looked like this amp was last serviced at jiffy lube.

Okay.  I'm breaking out the alcohol.  Here is a picture...

I have a Kustom "Frankenstein" style head whic I can't ID.  It does not appear to have any numbers on the PCBs.  It is very bare bones, two channels, Treb, Bass, Volume each channel, six TO-3 RCA transistors on the back labelled 36892. No "200" on the front plate, just "Kustom", but I am assuming that's what it is.  It looks all original, everything coated in a fine layer of grease, it works but has odd intermittent bursts of noise, kind of like an AM radio during a lightning strike, almost like dirty pots but it happens on both channels and is independent if turning any of the controls.  The controls do what they are supposed, volume makes it louder, bass makes it brassier, treble makes it trebly.  I haven't made any measurements yet, because I am hoping you guys might steer me to the closest PCB schematic. I assume there is a lot of similarity in the boards?

I have one of these that I got for $20.  It had a bad cap (the last node 10-350V on the power supply) and the two 22K resistors before it were bubbling and making a sound like frying bacon.  I replaced those, and now it appears to have all functions, although some of the controls are noisy (i ran out of deoxit and am getting some more). It also had a hole in one of the speakers ( I have the original peavey square magnet ones) which got the white-glue-tissue repair treatment. I also removed the two-inch palmetto bug corpse from inside the cabinet.  The cabinet is actually solid pine wood, the baffle is chip-board.  It also looks really convenient to work on if you had to, the ics are all socketed, there are a lot of connectors, so you could easily remove the board with just a couple of screws and the pot nuts.  All in all a solid piece of gear, I think.

Okay, it's not really a guitar amp, it's the power amp for a Kennwood Eleven GX, and it came with dead outputs and a bunch of burnt resistors, and after checking a number of other dead transistors.  Problem is where to find some of these transistors?

Drivers: 2SC1913, 2SA913

Also:  2SA733R (Q), 2SC1735, 2SC1845 (F,E), 2SC945R (Q)

I tried looking at MCM, but did not see any of these guys. 

A lot of the smaller ones are ECB.  I have the feeling there are things that would work with some leg bending.

Any advice on how to pick substitutes?

   

Quote from: Enzo on August 26, 2013, 02:45:00 AM
Isotap.  Is that the blue one with six outlets on top and a voltage switch, RCA brand?

Yup.  Mine was made by "Viz" but I think they are copies of RCA.  It even has the schematic silk-screened on the bottom.

I think this one you will have to make your own schematic.  It is only three tubes, however.  I have seen magnavox record players that had 12ax7 and 50eh5 and AC power, but I think those were stereo.  It does look you have dual volume control in there, but it is hard for me to get the whole circuit looking at fuzzy pictures.

From my days of playing with ac radio sets I have an 'isotap' isolation transformer.  Does anyone use those anymore?