Solid State Rectifier in PAS-2

Hi, I have not seen much mention of this. Has anyone swapped the rectifier tube for diodes in a PAS? If so, how did you do it specifically? And what do you think of it performance/sound wise?

Thanks!

Kinski wrote:Hi, I have not seen much mention of this. Has anyone swapped the rectifier tube for diodes in a PAS? If so, how did you do it specifically? And what do you think of it performance/sound wise?

Thanks!

Yes, it's perfectly doable.
I did it on one when installing a power board
( http://triodeelectronics.com/sdslacabofor1.html )
where i mounted a solder stand at the corner and 2 1n4007 diodes, bringing the HT
connectors to them.
As very low current flows no problems with hum, the power tranny will get a
well deserved relief when the 12x4 is removed.

Hey thanks! How exactly do you wire the diodes? Is there a diagram somewhere? And did you use any resistors to keep voltages down?

Kinski wrote:Hey thanks! How exactly do you wire the diodes? Is there a diagram somewhere? And did you use any resistors to keep voltages down?

=== red from transformer === [>| ]----- DC OUT--\
\
---- DC to CAPS
/
/
=== red from transformer ===[>|] -------DC OUT--

1n4007 [>|] note the line on the cap , this is the "anode"

See http://n.manet.nu/pas3/index.html scoll down to third picture

Both diodes mounted on a solder stand mounted on the corner of powersupply
No, no series resistor. It just works.

Hi, thanks so much for your help. Im a bit confused though. I'd be very grateful if you would help me out here.

The 12x4 socket is wired:

1: red/white lead from the transformer
2: nothing
3: To caps/diodes that used to be the selenium rectifier. Also to power switch.
4: To caps/diodes that used to be the selenium rectifier Also to power switch.
5: nothing
6: red/white lead from the transformer
7: to (newly replaced) CAN filter capacitors.

I get how to wire the two red/white transformer leads to the diodes, but what about the rest of the wires?

Kinski wrote:Hi, thanks so much for your help. Im a bit confused though. I'd be very grateful if you would help me out here.

The 12x4 socket is wired:

1: red/white lead from the transformer
2: nothing
3: To caps/diodes that used to be the selenium rectifier. Also to power switch.
4: To caps/diodes that used to be the selenium rectifier Also to power switch.
5: nothing
6: red/white lead from the transformer
7: to (newly replaced) CAN filter capacitors.

I get how to wire the two red/white transformer leads to the diodes, but what about the rest of the wires?

3 and 4 is filament. Let it be as you will remove the 12x4. And they don't connect to the power switch !!!

1 and 6 is the ones to connect to the 1n4007 diodes ( or un4007 is even better)

My mistake! Those leads from 3/4 go to the indicator LED, not the on/off switch!

Is there any reason I can't just remove the 12x4 and solder the un4007 diodes direct to the socket pins?

Kinski wrote:My mistake! Those leads from 3/4 go to the indicator LED, not the on/off switch!

Is there any reason I can't just remove the 12x4 and solder the un4007 diodes direct to the socket pins?

No there is no such reason.

Another even better option is to get a 7 pole connector mimicen a tube , solder the diodes on that and plug it into the socket.
Problem is to find one.

I replaced the 12x4 with the diodes. Easy. Im now reading 419vdc on pin 7. Manual says it should be 405vdc. Is this too high? I replaced the can cap with a new one.

I'm also about to install a thermistor on the incoming ac line. That should also knock the ac line down about 2v.

All good! Installed the thermistor and a fuse. Dropped the voltages perfectly. If anything, the voltage readings are a volt or 2 low now. Perfect! Thanks so much for your help!

Kinski wrote:All good! Installed the thermistor and a fuse. Dropped the voltages perfectly. If anything, the voltage readings are a volt or 2 low now. Perfect! Thanks so much for your help!

419 is no problem.
Make sure the thermistor don't get hot and not touching anything.

Thanks. All voltages are pretty spot on with the listed voltages in the manual. And the new filters CAN caps are rated at 475v.

I have the thermistor on a solder stand near the transformer. Has lots of room to breath. Fuse is underneath on the trace side of the PCB boards. Everything is running quietly and sounding great. Added bonus that the thermistor knocks a few volts off as well.

I just installed the VTA board into the Dynaco St-70 last week.

Made my own speaker cables as well today. Pretty much done modding stuff now. Although, I’ve said this before. Ha!

Thanks again!