72 fender deluxe

[rafe]

I have a deluxe that other than having had an intense and dense coating of dust, mold, nicotine soilent green , I dont know . (But that is now gone .) I had to clean it in the back yard before I'd bring it in AND that is saying a lot !!! If you saw my house..... Any way ,it's not mine and it's not for sale ....but I will be using it on a regular basis so I don't need to bring amp and guitar .....(Guitar is another story) I am doing this Pro bono there is a backstory ,but perhaps for another time. It's totally unmolested I'm sure I'm the first one in there 99.99990000% since it was built. I want to recap it but I also want to see if I can slowly bring it up first. I have an uncanny intuition on this one . all original RCA's. what are the chances this will live? what are the chances of damage. (pictures later) Oh Pressboard cabinet??? Thanks CBS card board shit !

[rafe]

Fired it up on the LBL no shorts....no noise plays good tone is good .only about 5 minutes . Should I pull the tubes and bring the voltage up little by little.

[rafe]

Everything has been cleaned up

[rafe]

More

[rafe]

last one cabinet was bad ...looks great now

[Platefire]

Nice old Fender! I'd change those filter caps first. then go over the whole thing with a fine tooth comb. Sounds like its been sitting up a while, I know those tube sockets, pots and plugs will needa good deOxit'ing

[rafe]

Howdy Platefire, I have explained to the owner that it is wise to replace the bias, coupling and filter electrolytics.  This amp has not been touched and I kind of hate to mess with it. I am wondering if He would be better off just relegating it to the back of a closet and leaving it be. He is a Hammond B3 and Leslie guy His dad is deceased and He has no need of this and his dads Strat, other than me doing a coffee night now and again. And I have amps . The GA-19 RVT is easy enough to transport. I am going to sleep on it and decide.

[DummyLoad]

Post some close-up pics of the lead ends of the electrolytics that are under the dog house.

--Pete

[HotBluePlates]

... Oh Pressboard cabinet??? Thanks CBS card board shit !

FWIW, Fender changed the baffle boards from plywood to fiberboard in 63-64, when they changed from brownface to blackface cosmetics.  Though yes, the rest of the cab being fiberboard & the baffle being not-detachable happened in the early 70s.

Also that Oxford 12L6 speaker is usually pretty sweet sounding.  I had a blackface Pro Reverb whose speakers were replaced with a pair of those, and it sounded so nice I bought some backups in case one ever blew.

[Platefire]

rafe
  I know what you mean. I once had a guy bring me pretty much original Marshall Plexi and wanted me to do some mods to it. I did it but did not like it. As I remember it, that was one of the deciding factors that caused me to get out of amp repair other than not making any real money out of it Platefire

[rafe]

Pete I am waiting for my phone to send them they are in the queue, but seem to be stuck there ......

[rafe]

as requested Pete

[mresistor]

the one on the right in bottom pic is pushing out the schmutz..     

[rafe]

such is so, Mister Esistor? It might very well have happened when I checked for shorts with the LBL , I don't remember seeing it before that. I went ahead and ordered the capacitors. I'll box up the old caps and send them back with the amp.I have a lot of them here now that I have saved ,however I never cataloged them so I only know where a few came from. The Shame.....

[rafe]

I changed out the filter caps and checked on the bypass caps , they were all passing DC enough for replacement . I have 2 more to go out of time tonight. I replaced the bias cap too it was passing a lot of DC I'm not sure if that is normal but I'll re-check later tonight when I return and finish the last 2 bypass caps . There was some noise on the pots less after cleaning but noise nonetheless. MWBR

[sluckey]

I changed out the filter caps and checked on the bypass caps , they were all passing DC enough for replacement .

What does passing DC mean? Is that current or voltage? How do you test a bypass cap to determine it is passing DC?

[rafe]

ck the dc voltage from one side neg to pos. I was told that was how to see if they were blocking DCv or not  a long time ago , was that BS?  any way the are being changed I'll check them again and see if I get the same readings???

[rafe]

HERE IS a Riddle. There are only 6 bypass caps in this amp 5@25-25 and 1@5-25 It looks like they left one out the 25-25 on v5 pin 3 the cathode with the 2700 resistor it's the vibrato tube. vibrato was ok. I guess mistakes were made in 72 I'm putting one in , right?

[sluckey]

ck the dc voltage from one side neg to pos. I was told that was how to see if they were blocking DCv or not  a long time ago , was that BS?  any way the are being changed I'll check them again and see if I get the same readings???

I wonder if you misunderstood what was said? I bet you will get the same or similar dcv with the new caps. If you follow that BS advice you will be forever changing those caps. 

It looks like they left one out the 25-25 on v5 pin 3 the cathode with the 2700 resistor it's the vibrato tube.

There should be a 25/25 cap across that 2700Ω resistor.

[tubeswell]

filter caps and … bypass caps… all passing DC

Filter caps and bypass caps both function to ‘make DC’ (i.e., they charge up with incoming current and are sized with sufficient capacitance so as to hold the charge for longer/release the charge more slowly - to the extent that the slower discharge rate and the faster charging rate work together to have the effect of holding the voltage at a fairly constant VDC. I.e., so that there is always DC present.

Coupling caps (on the other hand) are intended to block DC and allow changing current to pass across the dielectric barrier, and so they are typically sized to discharge more quickly.

[pdf64]

 … it is wise to replace the bias, coupling and filter electrolytics.   …

Electrolytic caps will wear out with prolonged heavy use and degrade if not charged up for long periods. So yes, replacement seems reasonable. But 60s onward film and ceramic etc coupling caps should last much longer, treat them as ‘replace on failure’.
If any are suspect, your cap test can be used on them to check for DC leakage.

[rafe]

DC Voltages across the caps dropped significantly on 3 caps. I think I may have been thinking of DC on the pots and confused the two things. However, DC voltages seem too high on initial testing. I checked a first 3 tubes and the power tubes . V1 pin 1 229v v2 pin 1 233v v3 pin 1 425 schematic shows 180, 170, and 410 the 6v6's were  v8 430v on pin3 v7 410 on pin3 (it squeals when being tested on v7))  schem. calls for 415v   Valves1&2 are microphonic when tapped  Volume and treble pots have a low volume swoosh when dialed  up and down. No crackle on any pots just the afore mentioned swoosh. Amp sounds good is pretty quiet but not silent. It's loud but I want to sort out the voltages and bias before running it too long I  made a milliamp meter and socket years ago from a tube base  so I will check that later today ....But I really don't want to run it long as is .....I appreciate any advice and/or direction on proceeding Thanks . I am going to put the newly reconed P12Q into the les paul for now and Truth be told ....I can't stop playing that amp (1952 GA-40) an although the P12N I temporarily installed is OK at low volume it has some issues and will be going in for a repair soon . I am really liking these early 50's jensens .......Thanks and regards Rafe.

[bmccowan]

Those are great amps - despite some of the dumb things CBS did. I suggest not worrying about hitting the schematic voltages exactly. +/- 20% is a common tolerance. I used to have a contracting business - our mantra was, "can't see it from my house." I'm pretty sure amp manufacturers have/had the same - even Leo. But the voltages should be relational across tubes and pins (not sure how to state this.) Replacing all the electrolytics is smart. One you are satisfied that you have found drifted resistors and replaced any faulty caps, one thing I can think of is that I have a Princeton Reverb of the same vintage. I do not really care about the originality value thing, so I replaced the plate resistors and grid stoppers with metal film. That helped with hiss. I also replaced those blue molded tone caps with fresh orange drops. I thought it helped clear up some muddiness, but I might have been hallucinating from the leaded solder fumes. And I replaced the Oxford speaker with a Weber Alnico. That amp sounds awesome with a Tele.

[66Strat]

What rectifier tube are you using? The AB868 Circuit shows a 5U4GB. If you are using a 5AR4/GZ34, that could account for at least part of the difference. Also, as has been mentioned before, Fender voltages published on schematics do not always reflect updates/corrections

[rafe]

"What rectifier tube are you using?"   It's The 5U4GB.I checked again after swapping the 6v6's to see if the problem followed the tube both read 420 vdc so that is much better and not a concern, all the resistors test good well within range. I have not checked the reverb yet. that will be next . The DR is a nice amp ....but if I had to chose I would
 take the 53 GA-40 over it at this point however I do like reverb so the jury is still out I am actually likeing Gibson amps in general. The P12Q sounds great and will just get better with age . Shout out to Bill In Landsdale