I would keep those tubes, they're the original Dynaco supplied Telefunken 12AX7 tubes, and should be fine.
Even if you don't want them, ebay will, but keep them. They last forever in the PAS.
1960's Telefunken Vintage Preamp Tube Ecc83 12Ax7 Test New #30 No reserve | eBay
Even if you don't want them, ebay will, but keep them. They last forever in the PAS.
1960's Telefunken Vintage Preamp Tube Ecc83 12Ax7 Test New #30 No reserve | eBay
Oh yes, definitely keepers. I just want to make sure I don't fry them with my lack of experience
Also don't turn on the preamp without all 4 audio tubes in the sockets. The filaments are series connected.
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I'm putting together an order from Allied Electronics, they have the 1N4006 in stock and I can buy in small quantities but the UF4007 can only be had in multiples of 100. Do I really need the UF4007?
Shopping for capacitors can be a little mind bending for a novice so I may have some questions regarding them as this project moves forward.
I understand that combining two caps of the same value in parallel doubles the capacitance, but what about the voltage rating, does this double as well?
I understand that combining two caps of the same value in parallel doubles the capacitance, but what about the voltage rating, does this double as well?
No, only the capacitance increases. The voltage rating remains the same. Avoid paralleling capacitors,
since the cost is higher, and the footprint is larger.
since the cost is higher, and the footprint is larger.
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I got the idea for replacing the selenium rectifier with the 1N4006 diodes from Curcio Audio Engineering website, they spec these specifically and even give a Radio Shack part number so I don't think CAE is making money on this mod. I'm curious why they would not have then spec'd the UF4007?
Hi Rayma, the logic was that he had bought a replacement multi section can cap that replaced the defunct one, but the first section was only 20uf, the old one was 30uf, and the tube could tolerate 40uf. Isn’t paralleling the first section a pragmatic solution?
The selenium rectifiers do gradually go bad and need replacement, along with the worn-out filter capacitors.
I've seen 10VDC on the filaments, with a lot of ripple. Those rectifiers are also toxic, so dispose carefully.
I've seen 10VDC on the filaments, with a lot of ripple. Those rectifiers are also toxic, so dispose carefully.
For the first section 20uF is acceptable, and was in the early Dyna preamps.
The bottom of the chassis is quite shallow for an added electrolytic.
The bottom of the chassis is quite shallow for an added electrolytic.
I ordered the 20/20/20/20 mfd can capacitor from Antique Electronic Supply. It is "Made in USA" by CE Manufacturing for $36.70.
The dynakitparts.com capacitor has the same values but the label does not indicate who makes it or where. It is $36.95.
Triode Electronics has the same CE Mfg. cap as AES but is $64.95
The dynakitparts.com capacitor has the same values but the label does not indicate who makes it or where. It is $36.95.
Triode Electronics has the same CE Mfg. cap as AES but is $64.95
after removing the pc boards and selector switch from the pre-amp, I now see what everyone has been saying about the quality of the PAS components. The chassis is extremely thin metal, it flexes with very little finger pressure. The 6 position rotary selector switch is so fragile, all of the "ears" that make contact with the plates on the wafers are loose.
There's not much I can do about the chassis, (maybe add some stiffeners?) but the rotary switch needs to be replaced. I don't feel comfortable rewiring the entire preamp only to have the selector switch fail at some point. There are ALOT of wires soldered to it.
So I'm looking for a replacement.
Dynakit Parts has this one for $7.00
There's not much I can do about the chassis, (maybe add some stiffeners?) but the rotary switch needs to be replaced. I don't feel comfortable rewiring the entire preamp only to have the selector switch fail at some point. There are ALOT of wires soldered to it.
So I'm looking for a replacement.
Dynakit Parts has this one for $7.00
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