• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

CJ PV-5 tubes

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#41
Here you go .

mmmalmberg said:
Funny have checked both and not found above 50 uF in 500V. Will recheck...
Click to expand...
50 mfd is close in this application or 100 mfd 2 section elec. Here you go Angela Instruments Online Catalog - Capacitors - Angela/ASC 50 mfd 515 volt . and 100mfd 2 section Angela Instruments Online Catalog - Capacitors - Electrolytics by Nichicon and Jensen.
Those cap get rid of some of the ripple be fore their regulator which is a cap multiplier .
My thoughts are replace the cap with that 2 section 100 mfd . Then work on an improved regulator to replace the 30 plus year old SS design . On that it depends how much you want to spend.
http://angela.com/electrolyticcapacitors.aspx
 
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#49
I know, I really hope to hear from someone who's done it recently enough to remember what specific caps they used🙂 Have email in to Ed at CJ as well as B. Thalman to see if I can get recommendations from them. Never know... They're made for you know the metal cans with tabs and the terminals solder right into the board. Hopefully tomorrow will hear something.
 
#51
Triodethom said:
Found a pohto of one Bill Thalman did that pre-amp was his baby while he was at CJ .
An externally hosted image should be here but it was not working when we last tested it.
Click to expand...

Some extra characters on the link but got it to work - thanks. So that looks like maybe two Solen FastCaps in series. That would account for how he's getting the voltage rating, since I'd been unable to find them in 500V.

I wonder if the two cans are in series in the circuit, in which case they could be replaced like this with film caps or with one good electrolytic. I wonder how the specs net out re. esr and ripple (and effect on sound) with something like two FastCaps (if that's what they are) in series vs a single, good quality electrolytic. I guess lifespan would be potentially a lot better with the film caps.
 
#52
mmmalmberg said:
That would account for how he's getting the voltage rating, since I'd been unable to find them in 500V.
Click to expand...

Clarification, I'd been unable to find them high enough capacitance in a voltage rating => 500V. And in the 630V range, they're enormous. Found out the answer for film caps here is to use a lower capacitance, evidently the performance of the cap in this position is more important than the capacitance.
 
#55
A couple and a half years later...

I did get the Solens in, along with a good population of tubes, and the preamp has sounded great. I just got a new Marantz cd player as well as a new AT440mla cartridge for my ttble, and everything sounds better than ever, except now the CJ has developed a loud hum. I can run the cd player's headphone out direct into the power amp (rebuild ST70) and no hum, btw.

I had only replaced the two 630V caps with Solens, so today I replaced the 4700uF 35V cap with a 3300uF 50V Nichicon (original spec 3300 25V) and I replaced the little 22 uF 50V cap with a new one same value. Hum is still present.

Hum: The hum starts at the end of the warm-up delay and then is loud, not affected by any of the controls, and is in both channels.

Should I suspect the diodes in the p.s.? Here I found some photos I posted from after installing the Solens discussed previously in this thread: Untitled Document
I don't even see any diodes, maybe they're below deck or are they maybe encapsulated in the little black box near the transformer?

Any other thoughts about likely culprits for this hum, given the p.s. caps have been updated?
http://www.markmalmberg.com/pv5/
 
#58
Thanks so much for your follow-ups! I hope to receive my stock PV-5 in the next week or so and am sure I'll follow a similar path as you have. My goal is to keep it original as possible, not interested in performance enhancements to a preamp whose original sonics are what made it a world class reference. Then again, I also find I enjoy 95% original LP pressings over newer remasters, so there's a hint at my value system for sound. Anyway, thanks again for your commitment to keeping this thread updated as you go, and good luck in working out the hum issue!
 
#60
I will mmmalmberg! It appears to be an ETA of ~6-12-15 when I expect to receive it so I will return, post the condition and tube selection, and perhaps compare notes with you if you're so inclined. I have my eye on the matching MV-50 that went with it. Both were purchased new and are said to have maybe 80 hours total on them and in absolute mint condition, so if I want the mate this is my chance to do that. Kind of a dream of mine since the mid-80's so I'm a bit excited to receive them and share the experience 🙂. Glad yours has fallen nicely into place and you seem pleased with the outcome!
 
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