1964 Fender Deluxe

[Johns62312]

I have a 1964 Fender Deluxe that hasn't been turned on in 15 years. I checked all the caps and they all checked good so I thought I would try it. Dead. Both the power and the standby switch were bad which I had to order. I put them in and it actually came and worked. I went ahead and replaced the ac line with a grounded one and replaced all the filter caps and the electrolytics on the board, they were really noisy. Now if you turn up the vibrato channel up to 3 or 4 and hit the strings hard it has a distortion on the peak of the sound. If you plug into the normal channel with the vibrato channel it still does it but if you turn down the vibrato channel it stops. All tubes have been replaced and it don't make any difference what tubes you put in it. Tubes are biased at 22ma. Tried different speakers to-no difference. Has anybody ever run into anything like this before. Any help appreciated. This was the first guitar amp I ever bought, got it in 1969 and paid 70 dollars for it. Would really like to get is goin and start using it again.

[plexi50]

Check the plate and mainly the cathode voltages to make sure all the preamp tubes are biased properly per each tubes cathode. That will tell you the preamp is biased. Then check the resistors in the entire amp to make sure they are within there spec values. Pic's?

[Johns62312]

I just now printed out the schematic for this. Think I'm going to call it a night on this. Better luck tommorrow.

[stratele52]

I  Now if you turn up the vibrato channel up to 3 or 4 and hit the strings hard it has a distortion on the peak of the sound. 

Check all the resistor on the Phase Inverter circuit . Wrong value = distortion .

Also bad solder .

A defective output transformer too. Do you have signal generator to test it ?

[Johns62312]

I have a generator but not here. I'll have to pick it up next time I'm over there. The normal channel don't seem to do it unless you turn up the volume on the vibrato channel. If it was a resistor in the pi wouldn't it do it regardless.

[stratele52]

I have a generator but not here. I'll have to pick it up next time I'm over there. The normal channel don't seem to do it unless you turn up the volume on the vibrato channel. If it was a resistor in the pi wouldn't it do it regardless.

You are right about PI .I'm Canadian french speaking, I have to read few time s to understand whant you write . I do some mystake.

IMO if vibrato channell induce distorion in Normal channel , you have to read some voltages on Vibrato circuit   V3 , 12AX7 and V1 normal channell to see what's happend.  Voltage drop ?  Check / reheat some solders and read the 220 K resistor and the 0.1 mfd cap at the exit of vibrato pots.

If we work on same schematic ; AB763


 

[HotBluePlates]

Is this the AB763 Deluxe? Without reverb?

Just making sure we know which amp circuit we're discussing...

[Johns62312]

That is correct, without reverb. Have 428v on the plates of the 6v6 with a negative 38.6 volts bias. The phase inverter has 202 volts on the 82k side and 193v on the 100k side with 77.1v on the cathodes-the resistor measures 550ohm so it's a little out of spec. Vibrato channel has 165v on the plate of first stage with 1.375 on cathode. The other side is 170.2 volts on the plate with 1.456 on cathode. The normal channel has 166.7v on 1st plate with 1.355 on cathode. Second stage has 173.5 on plate with 1.4556 on cathode.

[stratele52]

You have reverb ?

Same reading with Vibrato ( winch cause distortion ) .....

[Willabe]

You have reverb ?

He said without, without means no or not with.


       Brad     

[HotBluePlates]

That is correct, without reverb.

I don't know yet if we're missing an important clue, but...

The only common circuit point for both channels nearby to the volume control is the 2nd gain stage for each. They share an 820Ω cathode resistor and a bypass cap.

Look at your printout or this Deluxe AB763 schematic/layout. On the schematic, the shared cathode components are shown by a lette "C" inside a square. On the layout, it is pin 8 of each of the 7025's which have a wire connecting them and another running to the 820Ω resistor on the board.

Maybe since you replaced the electrolytics in the amp, the one at that 820Ω resistor has a cold solder joint or a poor connection to ground. Also possible is some oxidation on the sockets for those tubes (primarily the 2nd 7025, as it is for the Vibrato channel).

Thought Process: Noise with big signal peaks in an otherwise properly-functioning amp usually points to an intermittent connection, oxidized connection, cold solder joint or poor ground (these are all really variations of a poor connection). It always happens when you play the Vibrato channel, so doesn't seem connected to shared stages from the phase inverter to the output tubes. But it does happen when you play through the Normal channel with the Vibrato channel volume on, suggesting something shared by those but before the phase inverter. So it seems like V2 pin 8 and its components (the 820Ω and bypass cap).

It is odd it doesn't happen with just the Normal channel if these parts are at fault; maybe if you rule these out you'll stumble on another clue...

[Johns62312]

I just changed the bypass cap on the 820ohm resistor with the one on the 2700ohm in the vibrato circuit since they were side by side. I cleaned all the preamp and pi tube sockets hooked it up and it don't seem to be doing it anymore. I sure hope this isn't going to turn into one of those things that come and go, though it was doing it all the time. Some of these resistors are a little out of spec, how far out do you guys let them get before you change them out. I really hate to change to much, I already changed more than I would have liked but I really want to make this a useable gigging amp again. I want to thank everybody for the help, this is one great site.

[eleventeen]

On old Fenders, it can pay to examine under a magnifying glass the various solder connections on the parts board. (and everywhere else, of course) but the parts board connections in particular. I don't know what the MTBF of a solder joint is, but I have seen, more than once, a factory-made marginal solder joint achieve a state where oxidation forms around the wire and it simply ceases to form an actual "zero-ohm" connection to its tie-point. And reheating the connection, even with a tad of new flux/solder, often fails to cure the problem, because you cannot solder to oxidized wire. It's very tough to spot...most Fender parts-board solder joints take the form of "BBs" which is not ideal. But if you can spot the point where a wire enters the BB and the entry point is very slightly puckered, that's a candidate for a bad connection. It should *really* form a fillet. Most folks just reheat ALL the connections but that may very well not cure the problem.

[HotBluePlates]

I just changed the bypass cap on the 820ohm resistor with the one on the 2700ohm in the vibrato circuit since they were side by side. I cleaned all the preamp and pi tube sockets hooked it up and it don't seem to be doing it anymore. I sure hope this isn't going to turn into one of those things that come and go, though it was doing it all the time.

Awesome!!

You're probably fine. Little noises will pop up from time to time in a 50 year old amp, but if the amp used to make that noise regularly then you've probably solved it.

... Some of these resistors are a little out of spec, how far out do you guys let them get before you change them out. ...

The layout says all the resistors were 10% tolerance originally, and due to how manufacturers produced and sorted carbon comp resistors you're unlikely to find any closer than 5-6% on either side of the marked value (because they could be sold as 5% resistors for more money).

I wouldn't personally change any resistors unless they were so out of whack it stopped the amp from functioning properly. Like a 1.5kΩ that drifted up to 5kΩ or the like. And you're very unlikely to run into that. Instead, it is more likely that the resistors will eventually develop intermittent popping noises that are only cured by replacement with a new resistor (but finding just the one or two making the noise is tricky).

So to repeat, I wouldn't change any resistor unless there was no other way to make the amp function.

... And reheating the connection, even with a tad of new flux/solder, often fails to cure the problem, because you cannot solder to oxidized wire. ...

You're correct that you cannot make a good solder joint (any solder joint, really) to an oxidized surface. But the purpose of flux is to boil away oxidation to allow soldering. Given that, it seems like the rule we should use is to always add either some liquid flux to the solder, or new fresh solder (which has its own flux), when reheating old joints.

[eleventeen]

Yeahbut...there is oxidized---meaning the miniscule, irrelevant oxidation that occurs the instant a conductor is exposed to the air = perfectly normal and entirely solderable---and there is a level of oxidation that can occur on a 50-year old piece of wire that was never soldered particularly well in the first place. Talking about actual crystals, a dusty grey appearance. You've possibly worked on more old Fenders than I have, which is maybe 75 of them, but I can tell you that I have seen bad solder joints on old Fenders where the original factory-made connection never really flowed...the wire conductor somehow got surrounded by flux and while it somehow mechanically/physically made the "touch" electrical connection to the eyelet so that the amp worked and was shipped, the chemical, alloying reaction of an ideal solder joint never occurred. Fast forward fifty years and the wire conductor is now encased in crystallized flux and is no longer making a low-resistance connection if any connection at all. The conductor is badly oxidized to the extent that a "reheat" operation will not make a working solder joint without acid flux (which is a flaming no-no) or physically scraping it with a knife. You can heat and add rosin flux & solder quite a bit and never be able to achieve the alloying reaction. If the amp was stored in even a modestly humid situation for 15+ years, these flaky solder joints can definitely go bad. For this, you have to cut back the wire and resolder the whole thing.

[stratele52]

You have reverb ?

He said without, without means no or not with.


       Brad     

I know that a Deluxe have no reverb built in .

When john write ; " That is correct, without reverb. Have 428v on the plates of the 6v6 with a negative 38.6 volts bias. ......."

I thoug he said "with no reverb I have 428 volts ..... "
So I did not understand !!!

Di I said I'm Canadian french speaking . My english is poor .....

[stratele52]

That is correct, without reverb. Have 428v on the plates of the 6v6 with a negative 38.6 volts bias. The phase inverter has 202 volts on the 82k side and 193v on the 100k side with 77.1v on the cathodes-the resistor measures 550ohm so it's a little out of spec. Vibrato channel has 165v on the plate of first stage with 1.375 on cathode. The other side is 170.2 volts on the plate with 1.456 on cathode. The normal channel has 166.7v on 1st plate with 1.355 on cathode. Second stage has 173.5 on plate with 1.4556 on cathode.

Is this the reading with no vibrato , when working fine ?
We need reading with vibrato ON which do distortion .

[HotBluePlates]

Yeahbut...there is oxidized ... and there is a level of oxidation ...

I see what you're saying.

It wasn't an amp, but I've seen some oxidized component leads that were white and rough, like sandpaper. Dunno if the piece of equipment was in a saltwater environment, but it had some pretty extreme oxidation.

[Willabe]

Did I said I'm Canadian french speaking . My english is poor .....

Yes I know. I thought you didn't understand what without meant. I was trying to give you a definition of without.


           Brad   

[Johns62312]

Well, it came back. Last night I resoldered v2 socket then I unsolder and resoldered every connection related to it and it seems fine. Just got home from work today and went in cranked the crap out of it for about 30 minutes and no noise. Two nights in a row, maybe I got it this time. Keeping fingers crossed.

[stratele52]

Well, it came back. Last night I resoldered v2 socket then I unsolder and resoldered every connection related to it and it seems fine. Just got home from work today and went in cranked the crap out of it for about 30 minutes and no noise. Two nights in a row, maybe I got it this time. Keeping fingers crossed.

Fine , I'm not surprise , that is what I write october 28 ; solder.  This happened often in old amps.

[Johns62312]

I put a eminence wizard speaker in it and it actually sounds pretty good. I don't know how the dependability will be but I thing I'm going to give it a try.