Gretsch Amps

Another ‘which amp is this one?” Topic

26

Thx, Powdog ... I appreciate it .... I am not qualified to make some of these repairs myself. Only light stuff ... but I'm not afraid of trying either. I know at least one amp tech that likely could make these mods should they be needed plus my younger brother is an audio engineer in the music biz with access to some pretty good talent that I might be able to tap as well.

Next I'll dust off the inside of the cabinet and pull the reverb tank if necessary to ascertain that model number for sure. The schematics I'm seeing for a 6157 are showing 4 6L6s ... and I'm pretty certain there aren't any of those in there. There is only one fat tube ... I may be bringing up the Super Bass version of that 6157 schematic instead of what I need. That schematic also has a full wave diode rectifier too ... I believe that fat tube I see is the rectifier. Soo ... go figure.

Then I'm going to check to be certain that someone has not put a 20a fuse, paperclip or a piece of foil or something worse in the holder. There is no sign of melting in the upper chassis nor burn smell anywhere ... so hopefully that over fusing did not occur. Then I'm going to power it up and see which tubes are actually illuminating. I bought it outside on a deck in bright sunlight which made it difficult to see clearly inside when I powered it up ... plus there is a tube shield on one of them too.

To be continued ...

27

Interesting - I didn't know there were reasonable substitutes for the 6973.

Having had a ham radio license for a long time, and having along with a very modern SDR defined ICOM IC7300, several classic tube driven ham radios (some of which I had to do the restoration work on), I'm used to having to deal with extinct tubes. The worst are the TV sweep tubes that Swan, Yaesu, etc. used as power/final amplifier tubes, due to them providing higher power output (my Yaesu FTdx-401B will do 300 watts with 2, 6KD6 tubes), at a relatively cheap price at the time the radios were made (you could oftentimes go to the local drug store to get replacement TV sweep tubes). Sweep tubes (along with the infamous 7360, that was often used as a balanced modulator tube for voice communication) can be almost impossible to find, due to them not being made since at least the early 80s, and the complete and utter lack in many cases of direct substitute (designation number-wise) replacement tubes, or even substitutes that only require minor modifications.

28

So .....I dug into this gem a little more today. Some observations:

  1. Just by eyeball, the speaker looked to my untrained eye like the 12" in my Fender. Could not see the full number set. Nope ... C10R ... guess I ain't as good at 'eyeballing' as I thought I was. Humbling.

  2. Although I cannot make out the rating on the fuse, it is a tiny thin filament .. not like a big fat automotive one .. so it seems all good there.

  3. After dusting off the cabinet floor better, I could then see the 6157 model number. Thanks to Powdog for, among other things, pointing out the location thereof.

  4. As soon as I wiped down the lower chassis some, I could then see that the tube sockets have the tube numbers stamped right beside them. Guess the tube chart ain't gonna' be all that necessary.

  5. 6973 RCA power tubes. Looks like all the tubes appear to be original RCA issue.

  6. Pulled the speaker baffle to try to have a closer look at the cone because there is a slight stain on the grill cloth which concerned me. Possible that Rover substituted the amp for a fire hydrant at some point ... still checking into that. I have not yet separated the speaker from the baffle.

  7. Did not power it up bc the speaker is disconnected and I don't have any resister to simulate a load. Don't know if all tubes will light up or not yet.

  8. A few little dust bunnies in there ... no rodent residue or brown recluse egg sacks, thankfully ... but there is this powerful odor of what looks to be Carpet Fresh and a visible thick film of it on every horizontal surface. Gagging me ... disgusting, greasy feeling powder. Hell, it might even be conductive. I need a shower after that.

Finally, I wonder will it cause any harm to carefully vacuum out that cabinet and chassis ... or should I take it out into the garage, don my N95 respirator, and blow it out with my compressor or .... some other way? I have to have it clean in there.

So .. that's my story so far ... such as it is. Thanks so much for all the support. I'm grateful.

29

Amp is up and running now. All original tubes tested positive .. . Amp tech carefully straightened tube legs on the power tubes as he tested them, put 'em all back in and fired it up. No ambient noise and tone to die for ... different in all the inputs and very easy to shape. Love it.


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