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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Laffeyett PA 273 valve amp update help

Greetings,

I'm an new member, first post. I have a Laffeyett PA 273 valve amp that I want to use as a practice amp because of size weight and coolness...

It has been sitting some time and before putting into service I want to update some components.

- two 50 MFD 25 VDC Capacitors
- two (I belive) 270 ohm resistors near the power lamp [Red, Violet, Brown, Silver]
- the power cord

Questions,
1) What advice, suggestions, wisdom can you share.
2) I can not fond a schematic for this item. I was told that it is made by Sano and is a Sano 16W model. Still I can not find a schematic.
1 12ax7
1 12au7
2 6bq5's and
1 6ca4 rectifier

with a 12" speaker.

3) I was looking on https://www.mouser.com. What is the suggested replacement Resistor - Manufacturer / part number

4) What is the suggested replacement Resistor - Manufacturer / part number?
How about this?
Vishay Mouser #:75-TVAN1206.1
Aluminum Electrolytic Capacitors-Axial Leaded 50uF 25volts
2 $3.35


Photos available at:
Valve Amp - Google Drive

Regards
Domenic
 
Yes, replace the 50uF/25V caps (47uF caps will be fine there). You also should replace the power supply capacitors, and consider replacing the coupling caps as well. Do those resistors measure well? They are just providing a ground reference for the heater winding, they are almost certainly perfectly fine.

I couldn't find a schematic either, so it would probably be easiest to go from the pictures you posted.

You have a 0.05uF coupling cap and two brown tubular shiny coupling caps (I can't see the values). I'd probably replace these since they can really do some damage if they leak electrically. Someone has already replaced one of the old coupling caps with a 715Por 716 orange drop cap, so one has obviously already been a problem.

The power supply cap is the big multisection silver cap on the outside. I would absolutely replace it with a new one. (Antique Electronic Supply probably has an appropriate replacement). There are a couple of dropping resistors mounted to that cap, and while you are at Mouser you could order some new ones (Vishay PR-03 are fine for this application) so you don't have to worry about getting the old ones off in one piece.
 
Thank you for your willingness to help on this.

Looking at a shopping list, I am hoping to confirm the components you have pointed out.
I have added new photos that show the silkscreen info.
I labeled one of the photos (called labeled.jpg) Valve Amp - Google Drive

Can you confirm that I have this correct.

A) [G K] replace the 50uF/25V caps (47uF caps will be fine there).
B) [C] You also should replace the power supply capacitors, and
C) [E F] consider replacing the coupling caps as well. Do those resistors measure well? They are just providing a ground reference for the heater winding, they are almost certainly perfectly fine.

D) You have a 0.05uF coupling cap and
E) two brown tubular shiny coupling caps (I can't see the values). I'd probably replace these since they can really do some damage if they leak electrically.
F) [L] Someone has already replaced one of the old coupling caps with a 715Por 716 orange drop cap, so one has obviously already been a problem.
G) [Not sure which one this is] The power supply cap is the big multisection silver cap on the outside. I would absolutely replace it with a new one. (Antique Electronic Supply probably has an appropriate replacement). There are a couple of dropping resistors mounted to that cap, and while you are at Mouser you could order some new ones (Vishay PR-03 are fine for this application) so you don't have to worry about getting the old ones off in one piece.
 
AG & K, yes, 47uF caps. You'll want to buy axial caps, and you can buy higher voltage caps if that's all you can find. The higher voltage caps will be closer to the size of what you're replacing. The axial caps also usually have very long leads (especially the blue Vishay ones for some reason).

BC is not the power supply capacitor. M is.

C E, F, H, & I are old coupling caps. L is a new coupling cap.
G N is pointing to the dropping resistors that mount to the power supply cap.