Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: shooter on April 28, 2019, 03:56:02 pm
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been asked to go over a Fender Super Reverb, haven't seen it, probably won't for a few weeks, so I'm just oogling schematics in Doug's library. The customer says it's a '66.
looked at 270, 568, 763, 1069, I can only find dates on 2, both CBS ~ '69 notation on schematic. There isn't enough difference for me to pay much attention to as a fix-it guy, but would like to know, for knowing sake
thanks
dave
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If you are real lucky you may have a date stamp on the info sheet and/or tube chart inside the amp. Kinda like this...
(http://sluckeyamps.com/harvard/harvard_03.jpg)
Otherwise look at pot, transformer, and speaker codes for clues.
(http://sluckeyamps.com/harvard/harvard_04.jpg)
(http://sluckeyamps.com/harvard/harvard_05.jpg)
Google can tell you what the time stamp and mfgr. codes mean. You will also find that Fender changed their timestamp code method at some point and didn't always follow their own system. Have fun.
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Have fun.
Hopefully, I get a little twichy with other ppls gear that was new when I was :laugh: :w2:
I did tell the owner I didn't want the 50lbs of wood n speakers :icon_biggrin:
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In addition to all the things mentioned by Sluckey, the serial numbers stamped in the back of the chassis also provide a clue.
For a reference, see e.g. http://www.superiormusic.com/page195.htm
All in all, you can only know for sure that your amp is younger than all of the date codes (unless a part has been replaced...).
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Amp came in today! just as I was gearin up to finish my stereo! :BangHead:
no power 1st impression,
I hate fishpaper boards!!
smells like 1960's electronics should :laugh:
2 notations AB763 board, off to printer in morning
power cord is 2 pronger, frayed bad, leaving it 2 for now. Fixin the fray!
looks like 2 different hands have been inside n they did good, fix the broke, leave the rest.
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Found the 100 R PI tail R just stuck in the solder hole :think1:
It's hanging in space now so i'll remember in the morn :icon_biggrin:
The PA tubes are Ruby, "V7" is nice bright RED logo. "V8" is a burnt Red, near Brown. Plate doesn't look warped or burnt. I don't have any 1 ohmers!, got 2, 2W 10ohmers, gonna temp in for testing.
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Fixed tail R
Fixed power cord
added 2 bias R's
powered up n got #'s
bias was set at -55, left it for now
TAP A 472vdc
TAP B 470vdc
TAP D 413vdc
Idle current 23mA per tube, idling about 11W per tube, burr.
The Vibrato channel rocks, trem/verb work, about as loud as my 20W SE
The Normal channel is all wonky, no real volume, or tone control
scoping I get ~ 1.7vac into the left side TS, inside TS too small to scope. Ohming around yields about 300 - 500ohms to ground with nominal interaction from any knob.
Talked with customer, agreed to put new stuff in the TS/Vol, so ordering parts n taking the old out.
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Doug came through, I went to work.
Nor and Vib are now ~ equal, sounds good on either, just not quite right.
In the AM i'll raise the bias from arctic to sub-arctic n see if that moves me in the correct direction, otherwise, scope, which i'll use regardless, I just wanna play through a "mojo" amp 1st :icon_biggrin:
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Sending it to it's master
brought bias to -47, ~ 40mA/tube, TAP A ~447 rounds to ~18W / tube, 60%
Leaving it til customer evaluates since the tubes are unknown condition.
She did perk up, played 20minutes, made me smile dreaming of stardom :icon_biggrin: