67 Fender Vibrolux reverb question

gtmcgar1

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I'm working on a Vibrolux Reverb that had some noise issues. Found a bust tube pin in v4 socket so the 'new' tube missed the mark, anyway I think this is the AA964 schematic based on the serial number and date code 1966 stamped inside the doghouse. Im not an expert on vintage Fenders wondering if this is a true 66/67 BF Vibrolux reverb or some hybrid.
The amp has had a few mods and some 'work' my question is should I reverse the 'mods'?
Also the dropping Rs are 10k,20k not 10k,10k as in the schematic. Any suggestions here?
Haven't had power on the amp yet based on some issues so far, broken PS cap, frayed wiring to doghouse and a few other issues, also waiting on parts.

thx g
 

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Jon Snell

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Incompetent personell incorrectly forced the valve into the wrong side of the socket, easy to remove the broken pin and straighten the retainer.
When the last person fitted new capacitors they were not dressed correctly and vibration took its toll.
Mods; Is that after the phase splitter I wonder. Without detail or sight of the amplifier, I can only guess, so not any help there.
The power transformer looks like it has been rewired for a different primary voltage ...

Nice amps when working properly.
 

Phrygian77

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I've been curious about the axial leaded JJ caps. I personally haven't seen them used by anyone. The weld shouldn't just snap like that on a relatively new cap, even if there wasn't much slack left in the lead for expansion and contraction.
 

AntonyB

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Hi,
Yes you'll definitely fix that broken leg from the electrolytic in the doghouse.
I don't know which music you are playing but those orange drops as coupling caps will change the original tone if the amp. If you have the original blue molded caps, I would put them back there. If not, you can use the reissued Jupiter or the sozo molded (check what they have a mojotone or amplifiedparts/antique electronic supply.
Regarding the tube pin holder, yes, clear that up and retense them.

For your dropping resistors, keep that there for now, but measure the plate voltages as you bring the amp up (you have a variac?) If it's out of whack, yeah, change back to 10k. But I wouldn't sweat it until you can actually measure the voltages. All Fender schematic say values at +/- 20%... they are pretty tolerant in general.
And a 20k instead of 10k would reduce voltage even further anyways...
 

schmee

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I would reverse the mods and go from there once that is done. It appears the PT has been replaced at some point, measure for appropriate voltages. They often run very high though even stock.
You can likely resolder that filter cap lead.

That one 9 pin socket is pretty rough other than the broken pin in it also. You may end up replacing that unless you can make those pin holders more uniform in shape.
 

schmee

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I've been curious about the axial leaded JJ caps. I personally haven't seen them used by anyone. The weld shouldn't just snap like that on a relatively new cap, even if there wasn't much slack left in the lead for expansion and contraction.
I used some recently. I guess a cap is a cap as long as they last. Hard to say at this point. They do have more of a large body size, and heavy lead thickness more like the originals...
 

Wally

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That PT date code does not fit the rest of the amp. That PT is from 1971 at the earliest. Also, the model code is not listed as a VR power transformer. The export PT for a VR is #022371?
 

gtmcgar1

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Well some great inputs, I haven't done anything yet but just at the planing stage. The JJ caps were stressed somewhat and someone removed the foam strip inside the doghouse to allow them to fit, the board is badly buckled. Anyway thanks for the inputs.
I'll look for Sozo molded and take out the orange drops, I like that idea.
Return amp to stock AA964 schematic.
Replace bad socket and rebuild the doghouse, I'm not going to mess with the JJs.
Also like the idea to stay with 20k dropping R especially since its a replacement PT.

Thanks guys I'll keep you posted.

g
 

rdjones

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I'm working on a Vibrolux Reverb that had some noise issues. Found a bust tube pin in v4 socket so the 'new' tube missed the mark, anyway I think this is the AA964 schematic based on the serial number and date code 1966 stamped inside the doghouse. Im not an expert on vintage Fenders wondering if this is a true 66/67 BF Vibrolux reverb or some hybrid.
The amp has had a few mods and some 'work' my question is should I reverse the 'mods'?
Also the dropping Rs are 10k,20k not 10k,10k as in the schematic. Any suggestions here?
Haven't had power on the amp yet based on some issues so far, broken PS cap, frayed wiring to doghouse and a few other issues, also waiting on parts.

thx g

Fender (CBS) PN# 014955 is the export power transformer for tube rectified 2x6L6 amps beginning around 1980-1981. This includes the Fender 30 and Vibrolux Reverb.

The presence of blue moldeds and date codes indicates, to me, that this is a modded and "serviced" blackface VR.

I'd first correct the known issues - the cap, socket and any frayed wires.
Then bring it up while monitoring AC current and run a voltage chart.
 

rdjones

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Well some great inputs, I haven't done anything yet but just at the planing stage. The JJ caps were stressed somewhat and someone removed the foam strip inside the doghouse to allow them to fit, the board is badly buckled. Anyway thanks for the inputs.
I'll look for Sozo molded and take out the orange drops, I like that idea.
Return amp to stock AA964 . . . .
Not really needed, depending on which Orange Drops they are.
Are they marked with a Sprague series number such as 225 or 418 ?
Certain ODs from early on were internally identical to the construction of the blue moldeds (polyester film and foil).
This is part of why ODs were chosen at the beginning of the Smith/Rivera Fender period for audio caps.
 

gtmcgar1

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Thanks for the PT info this helps a lot. Orange drop caps are a mix of CDE418 and CDE715 I'll noodle this for a while, still waiting on parts. The sockets I ordered were not great quality I'm looking for something better. The mod looks like the RobRob normal channel reverb mod that adds Trem and reverb to the normal channel, I still think I'll reverse it when I decide on the caps.

thx again all inputs appreciated.
 

SnidelyWhiplash

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I would bring the amp back to stock & fix it. Don't be too hasty to replace the ODs. I have a Princeton clone full of them & the amp sounds fantastic. Let your ears be the final judge. If it sounds good to you, great. If not, then replace. No one is gonna know what caps you use. Hidden away inside the chassis. :)
 

gtmcgar1

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Starting to get things back together, still have a few questions hopefully I'm on the right track now. Rebuilt the doghouse and cleaned up the socket issue, had to replace v3/4 they were trashed beyond. Voltages as follows, do these seem ok or do I need to revisit? I'm assuming these are off slightly because of the non standard PT.

6L6 pin3 440v
B+1 410v
B+2 408v
B+3 316v
B+4 276v

V6 pin6 183v
V6 pin3 78v
V6 pin1 183v

V5 pin6 388v
V5 pin1 442v

V4 pin6 194v
V4 pin3 1.4v
V4 pin1 191v

V3 pin8 8.6v
V3 pin1/6 442v

V2 pin8 1.1v
V2 pin6 155v
V2 pin3 1.6v

V1 pin 6 276v

Also found a cap installed backwards unless I'm missing something, was told the amp was working fully (just noisy) doesn't make sense to me?
Any inputs welcome, cheers


IMG_3800 2.jpg

IMG_3822 2.jpg
 

Wally

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That plate voltage on the 6L6s is high for a VR. That must be attributable to the PT, which is one I have never seen. The lower B+ voltage that a VR should have is the thing that I like about the VR in comparison to the other 6L6 Fender reverb amps. I will take note of that PT and the years that it was used. Thanks to @rdjones for that info and to you for the voltage chart. Imho, this voltage difference mak3s the older VR more valuable to me. Ommv. Regarding the preamp, your voltage numbers are incomplete for the V1 and V2. That V1P6 voltage is way out of line.
 

milocj

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Is that backwards cap even soldered to anything on the one end. It looks like it may have been installed backwards and they just cut the one end loose to get the amp operating correctly.
 

Wally

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Also found a cap installed backwards unless I'm missing something, was told the amp was working fully (just noisy) doesn't make sense to me?
Any inputs welcome, cheers
I would install a new cap there in place the other 25/25 in that area. The manner of making that connection to the ground side is questionable at best. I would question everything that was done given that level of workmanship.
 




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