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Help with pro reverb amp restoration.

Discussion in 'Amp Central Station' started by Hunter88g, Nov 27, 2019.

  1. Hunter88g

    Hunter88g TDPRI Member

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    Hi guys, I'm new to this page and along with electrical components. I'm wanting to learn so I can get my pro reverb amp up to specs. It needs new filter capacitors for sure. Two are leaking from the original Mallory capacitors... now I've seen a kit that resembles the exact values on Amprepairparts.com (AA-1069 pro reverb model FCK-BA kit) but I have no solid experience with schematics on this level. So far I can only identify the 5 filter caps in the doghouse, and the 6 25/25 caps coming off the knobs. All the resistors and one other cap I have no damn clue where I'm looking for to change out. Anyone have an easy breakdown for changing these out?

    (Also yes I am being safe and am aware of the shock hazard.)
     
    Last edited: Nov 28, 2019
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  2. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    First of all, can you tell us more about your amp? Maybe show a picture?

    Looking at that page and the cross-reference for the amp model, you would want the FCK-4B kit, rather than the 4A.

    I think the resistors are to go along with the caps in the doghouse (the 5 filters you mention). I am not sure what you mean about caps 'coming off the knobs'. Another one of the caps is likely the bias cap, found close to where the pilot light is in the chassis.

    This might be a job best left for a tech?
     
  3. Stax1

    Stax1 Tele-Meister

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    Honestly dude, unless you're gonna do this stuff under some tech supervision, I'd suggest finding a tech to do it for you. If you want to learn so you can do it yourself, ask if you can be there when they're doing it. My amp tech is happy to work in my amps in my presence and talks me through things as he works - great learning experience - but I prefer to leave those things to him. I'd be happy to change out a pot or input jack, but other than that I yield to his expertise. Its too risky, and ultimately I just wanna play the thing..

    Also, filter caps don't require frequent changing, and it'd be worth them inspecting the rest of the circuit for issues at the same time.

    Just my opinion of course!

    BTW - Pro Reverbs are great amps! I have a silverface flavour. :)
     
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  4. Mexitele Blues

    Mexitele Blues Tele-Afflicted

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  5. Hunter88g

    Hunter88g TDPRI Member

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    Alberta, I can post pictures. Which I'll do.here shortly. And I want to ask why do say the FCK4B over the 4A from you?

    STAX1, I appreciate the concern. I really do not know jack but I've got a multimeter and know of the need to discharge capacitors. So this will be a learning experience but I ain't planning on kicking the bucket over it. All the same thanks man.
     
  6. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Well the 4A seems to be for SF Twin Reverbs... I used this link: http://www.amprepairparts.com/capkits.htm#crossref

    And I scrolled down to the Pro Reverbs... it said this:

    Pro Reverb AA165 (1965) FCK-4
    Pro Reverb AB668 (1968) FCK-4C
    Pro Reverb AA1069 (1969) FCK-4B
    Pro Reverb AA270 1970-1972 FCK-7

    So it really depends what year/circuit you are actually looking at. And I hope you aren't merely going by the tube chart pasted inside the cabinet, as those are notoriously wrong. This is why I think you should post a lot of pictures of the amp you are planning to be working on.
     
  7. Hunter88g

    Hunter88g TDPRI Member

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    20191127_202724.jpg
     
  8. Hunter88g

    Hunter88g TDPRI Member

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  9. Hunter88g

    Hunter88g TDPRI Member

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    20191114_154203.jpg
     
  10. Hunter88g

    Hunter88g TDPRI Member

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  11. Hunter88g

    Hunter88g TDPRI Member

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  12. Hunter88g

    Hunter88g TDPRI Member

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    So the 6 25/25 caps are the white caps in the chassis I was talking about coming off the knobs/pots (assumingly)
    And i am only going off what i could find in the fender schematics. So mine is supposedly at 73. And the only schematic with a 5U4 rectifier matching up is the AA1069 close to that year, since someone In the past scratched out the chassis number. And the transformer #s are all over the place I cannot be certain. Also I can identify the bias cap but it doesnt match up values with the kits I've looked at. I can post more pictures later. Just need to know what specifically to locate and change.
     
    Last edited: Nov 28, 2019
  13. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Does your amp have a master volume knob?

    The AA270 also uses a 5U4GB rectifier, and if your amp is from 73 (or later) then it is not an AA1069. The way these circuit designations work is the last 2 digits are the year, and the digit or 2 before that is the month. So AA1069 is from October of 1969, and AA270 is from February of 1970. And in general, the amps made from that date until the next circuit designation falls under that circuit.

    https://schematicheaven.net/fenderamps/proreverb_aa270_schem.pdf

    If there is a master volume, you might be looking at this schematic:

    https://schematicheaven.net/fenderamps/cbs_45w_mstrvol_pullsw_super-pro-bmstr_rev.pdf
     
  14. schmee

    schmee Doctor of Teleocity Silver Supporter

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    -Get Filter caps with 500+ volt rating and as close to what's in there as you can. You need 70 uf x2, and 20uf x 3 (you may find 80 uf and 22 uf easier to find and they are fine) 450 v for the 70 uf are fine. Note that the two 70uf caps go different directions on the board!
    https://www.cedist.com/products/capacitor-ft-500v-axial-lead
    https://www.cedist.com/products/capacitor-ft-450v-80-f-axial-lead-electrolytic

    -Get common Sprague 25uf 50Volt caps for the 6 coupling caps. Going up to 50V is a good thing. Be careful, one of those coupling caps is 5uf-25V rated in the SF amps. (Left hand end of your picture in post #7) Get 50 V for that one too if available. These replace the white caps on your board. The crimped end of the new caps go toward the back of the amp. https://www.cedist.com/products/capacitors?filters=Brand=Sprague Atom

    -The cap on the little bias board: get something rated for 100v or 150 v. 50uf to 100 uf.
    https://www.cedist.com/products/capacitor-illinois-100v-100-f-axial-lead-electrolytic

    Be sure to double check your amp that the above are appropriate. Not a MV right?
     
    Last edited: Nov 28, 2019
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  15. Hunter88g

    Hunter88g TDPRI Member

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    Alright so here's all the pictures i should have sent last night.

    Since there isn't a master vol. The back of the chassis says 73' and most earlier models say "pro reverb amp on" on the faceplate ...I think this amp is an AA1069... but that's why I'm here to verify it, and fun fact the person I bought it from said it was a 68' haha. Chassis number is scratched to **** but I "think" I read A-10334. I can definitely make out the A-1***4
    Has those oxford speakers CBS era. But we dont have to get into that.

    So once we establish the right schematic for this map. Let's move on towards the proper capacitor and resistor locations. As I stated earlier, the 5 filter caps in the doghouse and the 6 white caps in the chassis I've located minus 1 cap in the set a (4.7uf 50v). As far as identifying the resisters for this FCK-4B cap set I have no clue which is which.
     

    Attached Files:

    Last edited: Nov 28, 2019
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  16. muscmp

    muscmp Tele-Afflicted

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    yea, sure seems to be a 73 based upon the transformer numbers. what numbers are on the oxfords? some people like them and some don't. don't make a decision on them until you have the amp up and running again for a while. that should end up being a great amp.

    play music!
     
  17. King Fan

    King Fan Poster Extraordinaire

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    Your good pics and the good brains here basically have this sussed. The question now is — why bother with a kit? I’d look at what’s in there now, upgrade voltages and if needed capacitance as @schmee suggests, and see if I couldn’t source replacements a la carte from a single source. You just don’t want to have to sort out the thousands of cap variants out there from a huge electronics source.

    If a guitar-amp-specific smaller source like Doug Hoffman has the right values, his nice F&Ts in the doghouse and nice small Nichicons in the chassis would be at your house in a couple days at very reasonable cost. TubeDepot is also pretty amp-specific.

    Resistors may very well be fine. It’s worth testing any that are isolated in the circuit, especially those near heat (sockets). Note you can’t directly test those that are part of a pair with a capacitor — but you’d be unpairing them when you replace the caps. [emoji846]
     
    Last edited: Nov 28, 2019
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  18. schmee

    schmee Doctor of Teleocity Silver Supporter

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    I had a 68 Pro Rev with Oxfords. They were real ratty so I sent them in for accurate recone . At the time Orange County Speaker was still reconing and they were amazing at that. When they came back I couldn't believe it. They were big and bold with great low end.
    Sometimes we forget that speakers we complain about are 50 years old! The perimeters on these felt soft like Kleenex. They were firm when they came back. Those perimeters must flex millions of times in 50 years.
     
    Last edited: Nov 28, 2019
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  19. muscmp

    muscmp Tele-Afflicted

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    tube depot, amplified parts and mojotone as well as others are having black friday/cyber monday sales so now could be the time to get the necessary electrolytics and replace them.

    play music!
     
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  20. Mark

    Mark Tele-Meister

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