开云体育

"glad to hear the DC/DC converter is working that should be a relief.
so why is the Ac-Dc linear causing an issue??"

I found out it's not. It's the voltage.

"The Chopper xsistor is not too important which were my original thoughts prior to over thinking a replacement. It appears the venerable 2N3055 should be fine."

I tend to concur now that I know how slow they chop. I don't know about a 3-55 but hell, it might. What I don't see is an easy way to mount a TO-3 in there, maybe a TO-3P or whatever, some sort of flat pack type should be fine and they are available now with specs just as good if not better. A TO-220 would be great as long as one can be had with good enough specs, perhaps a 2SD401 ? We used them for just about anything. Not real fast but we apparently don't need real fast.

Either way, switching time is not causing the excess current drain, and neither would high saturation voltage. Now listen to my latest conclusion on mine, the waveforms :

At ~16 volts in;

50 uS /g/TekScopes/photo/44484/2?p=Name,,,20,1,0,0

~17 mS /g/TekScopes/photo/44484/3?p=Name,,,20,1,0,0

Now at ~30 volts in;

50 uS /g/TekScopes/photo/44484/4?p=Name,,,20,1,0,0

~17 mS /g/TekScopes/photo/44484/5?p=Name,,,20,1,0,0

At 16 volts in it runs cool. At 30 volts in the heat builds up fast. In both cases the AC transformer was completely disconnected and out of circuit.

The 16 volt readings were using a full wave rectified source running into 10,000 uF external filter, in a Kelvin type connection. About 1 volt P-P ripple.

The 30 volt readings were using a full wave rectified source running into 1,500 uF plus the 2-1,300 uF in the Tek PS itself. About 3 volts ripple.

No heat buildup at 16, fry eggs at 30.

Looking a the waveforms, at 30 volts there is so much disturbance at the collector of Q 1174 the scope won't sync. At 12 volts it syncs fine. The "slo" waveforms were with the sweep down to match the ripple. At 12 volts you can see an aberration at 120 Hz, at 30 it seems to be random and looks like arcing actually. (I am familiar with that look from the TV days)

If I were you I would look for similar aberrations in the waveforms in that unit. It is a simple matter of slowing the sweep. You can take it to some factor of 16.67 mS if 60 Hz where you are, or 20 mS if 50 Hz. This allows you to isolate the ripple and the error correction involved. Just rock it in free running. If you see what I saw at 3- volts in, your problem is similar at least.

However I can't call it an arcing T 1201 yet. The drive has top be ruled out and I am not sure how to do that. The base waveform is no doubt susceptible to the Miller effect and that will even affect the waveform at the primary of T 1171. (in an HOT or LOPT circuit the effect is very profound) I think that means the ripple is responsible for the aberration in the chopper waveform at 16 volts input, especially since it reduces when the 10,000 uF is bridged in parallel with the input.

T 1201 is still a prime suspect, the voltages going to the drive circuit are regulated, (have to make sure of that of course) while the voltage into the primary of T 1201 is allowed to vary with the input. Unfortunately I think I am going to find T 1201 bad, and I think the chances of getting one are about the same as me winning the gold medal in Women's gymnastics.

It might be a DC only scope now...