On Apr 19, 9:37 pm, EricM wrote:
On Apr 17, 6:35 am, Heinz Schmitz wrote:



EricM wrote:
BTW, what is connectors 2 on CR4 and CR5?
Does somebody switch from 8 to 2 at some point?

The 1N1239 was a replacement for the
5R4 vacuum tube rectifier;

Oh, that explains it. Then the 5R4 ist a directly heated rectifier
tube and the 5 Volts AC are the heater power. This is, you may
disconnect 12 and 13 from the mains transformer when usingseleniumor other semiconductor rectifiers.

I also located another online vendor that
sells 'C-Cap' rectifier replacements and he states that his 5R4
replacement should work. I'm debating whether or not to order some to
test though,

Investments into faulty equipment mostly turn out wrong, if a sound
reason for the purchase is not present :-).

And essentially what the relay does, is shunt resistor R5,

To give the amp tubes time to heat up before anode etc power is
applied. Very reasonable.

as pins 2
and 8 seem to be looped no matter what position the relay is in. This
one is really a pain - I've never encountered a PS like this one...

It looks quite ok once we understand everything :-).

Now, once the power supply seems to be ok, I would follow the 600 V
wiring into the amp with an Ohm-Meter and try to locate a low
resitance to ground.
Next I would check all anode-to-grid caps like eg C19 at V8b. If some
of those leak, the grid will not be negative enough and anode current
will go through the roof.
I'd disconnect T2 on the primary side and measure the resistance of
the windings and the resistance to ground, to prove that the
transformer is still ok.

Well, much everything like in a common radio repair :-).

Regards,
H.

Actually made some progress. Yes, a previous poster was correct that
my understanding is "sketchy" That's why I'm posting here...

I didn't replace the large Sarkes Tarzians, but did replace theseleniumstacks. I do intend to put 5R4's back in the PS for
rectifiers though, as due to their age they may be contributing to the
overvoltage in the 600V circuit (i.e. reading 900+ when all's supposed
to be present is around 600). Have since found out from another tech
that the silicon's I used elsewhere in the PS circuit are no problem
since they're not part of the HV circuit, and their output voltages
under load measure normal. Will add a small dropping resistor though
to prevent damage to the tubes. One problem was that there was a cap
in the 600V circuit on the amp side that was conducting - basically a
600V to ground. Not good, and was causing the fuse to blow. Replaced
it and got the amp functioning and not blowing fuses, but after
applying a test signal from a tone generator, something 'opened' and I
am getting some 60 hz buzz in the output, which I think might be one
or both of the two 80/450 caps in the power supply that were damaged
by the fuse blowing several times during troubleshooting. In
addition, I did find that two other caps in the amp were getting bad
(old can electrolytics) - made "new" ones and things got better, but
still 'buzzing'. I also suspect some of the old can caps (lower
voltages) in the power supply in addition to the large 450V units, as
at this point there isn't anything else in the amp that is old and
could be shorting or leaking. All of the signal caps have been
replaced with Auricaps. Been a lot of work, but I think I'm close to
completing the project.

Forgot to mention that the 'buzzing' only starts after the relay
closes - so more evidence that it's either the 80/450's in the PS, or
possibly a problem somewhere around the voltage divider/0A2/6DR7
portion of the circuit that is fed from the 600V terminal in the amp.