Hi all,
I’ve got a PS-2A that has extremely low volume in any fashion that I try to use the amp. Through the Efx Return, Amp in, and Line in. All the same issue. I’ve tried replacing the tubes but no luck there. Is there anything I can check? I know that Diode 201 and 202 were open as well as the ceramic caps right next to them that run to the output transformers blue and brown. I’ve checked resistors on the board but can’t find anything else that is open or out of tolerance. Any ideas?
Hi Devintautry and welcome!
Are you having a go at repairing this yourself?
If you want to send it to Fryette or to a local shop for a service, then please follow these links:
I cannot really comment on your repair work because it is a very open-ended question. If you want to ask something more specific, I’d see if I can help. I’d recommend sending it in for a service following the above links.
Regards,
Hey Dan,
Thanks for responding. Really all I need to know is what are the diodes at these positions and can I order new ones either from you guys or is there a replacement that is comparable to what’s there? I can’t find these diodes anywhere. It’s labeled V70 R5000
It’s a R3000F high-voltage diode.
Awesome thanks! From my understanding it is what keeps a bad tube from frying the OT. So I guess the previous owner had put a pair of bad tubes in it and caused it to short. At least that’s my guess. The Screen resistors were reading fine and within tolerance but pulled those out and putting them back in brought current back to the tubes. I have a PS-100 as well and used the diodes from it to check everything was working after what I did. Thanks for finding the value to that diode! Couldn’t find it anywhere! I’m able to find your value. Thanks Dan! This topic can be closed if that’s a thing.
I’m not sure you’re on the right track with your diagnosis.
D201 and 202 usually read open as will the capacitors in parallel. The only time you would consider replacing those is if they are shorted. I’ve never seen a failure of either of those diodes or caps in a PS-2, so I would put those very low on the watch list.
If shorted power tubes are installed, the first thing that will most likely happen is a blown internal fuse.
If you have plate voltage but no current, you need to have something plugged into the speaker jack to enable the power amp to operate. If you do and still no plate current, something is amiss in the bypass switching circuit.
Is the fan operating?
Dave
Yup, the caps (i think 471k) where both open as well.
I always have a speaker plugged into the powerstation when its on just out of habit.
Fan is operating
I did see the video the one guy posted about the one 2 or 3watt resistor on the main board being burnt. Either it was that or the zenner. Might be mixing 2 videos up. But checked all over that board and everything seemed to be ok.
Ill keep an eye on it for sure. But it is working now.
One thing i did notice is that there is current to thw tubes even when i first power it up in bypass mode. Usually its just the plate that comes up and when its off bypass then the current comes up. Was about 30 mA i think which was about 11watts. When i flip the bypass it hits 20 watts dissipation on the tube. So its something ive been trying to track down after the current came up.
Thanks for the info, anything helps since we dont get to have schematics 
How did you measure the caps and the diodes were open?
It is unusual that all components failed in the same way.
The diodes often measure open on a typical DMM in diode mode because the voltage drop is a lot higher than say a 1N4007. Anyway, if you’re not blowing the internal fuse with no power tubes installed, there is no reason to look at those diodes and caps.
The PS-2 doesn’t have the Zener bias regulator, by the way.
And the tubes draw very little current in bypass mode because the power amp goes on standby when in Bypass.
Now you say it’s working, so it’s much more likely something simple such as oxidation on the FX return jack. If the volume drops again, try jumping the send to the return to see if that restores the volume.
If you have something connected to the loop, unplug that and see if it’s level or ground loop related.
Dave