Recent content by 50 Green

All I can say is you must be a glutton for punishment! (It's a couple of weeks too late for April 1st, so you can't be setting us up for a joke...) So it worked before you fixed it and doesn't, once you did? The problem occurred after only replacing the one resistor? You checked your work...

Nice setup. It's great to see your grandmother's 7065 up and running!

Great news! Your patience and careful, methodical work have paid off!

I was suggesting to test the zener diodes with the resistance function of your DMM (ohms, not volts.) That should at least show if one failed short. Is the difficulty of testing Q806/Q807 due to difficulty accessing them with your meter's probes, or due to readings being affected by adjacent...

To start, just test the zeners with your ohm meter in circuit. Let's see what that shows, first.

I checked previous posts, and in post 140, you mentioned getting a bad reading on D807. Did you ever confirm whether it was bad, and if so, have you replaced it already? Also, since Q802 was in wrong, it wouldn't hurt to check D801 and D802, as well as Q806 and Q807 on the "Control Board."...

Perhaps D753 was affected by Q755 being in wrong. Good you checked. From what I see online, and comparing datasheets, 1N4004 should be a more than adequate replacement. 1N4001 should even be comparable, but these diodes are cheap so I'd prefer to install the more robust version. If you don't...

Great that you're learning your way around the circuit! DBTs serve two purposes. They light up bright if there's a short, so you can kill the power and (hopefully) save adjacent components. They also limit the current, helping to prevent damage. Hopefully no harm occurred during the time you...

It's a good sign that all the transistors you pulled tested as good. There may not be extensive damage from the original fault. Have you powered up only on the DBT, since you replaced components? (That would help limit any further damage from anything being in the wrong way.) I don't recall...

The trimpots could be bad but I don't think they'd be the cause of anything you're seeing right now. With the components you have currently removed, you should be able to test them in circuit. They're 10K linear taper, so if you put one test probe on each end pin, turning the adjuster should...

Learning is good! Did you get the +42.6V reading on the black pin with C706 removed?

Au contraire... C706 is a direct link (via R715 and RT701) to higher, positive voltage. That's why I asked whether RT701 changed the voltage any (30mV is actually a substantial change) and whether your transistor tester could check capacitors, also. I hesitated suggesting you remove and test it...

Ah! I see you posted as I was typing the previous reply. Great that you're getting some insights, better materials, and good practice! Was that C704 on the 7065's board? Is the 42V with C704 removed? (That's POSITIVE 74V?)

Here are some thoughts... There are some variables I think you might want to consider in deciding how to proceed with this repair. What was the condition of board when you started? From your photos, it appears that at least the snubber capacitors in the rectifier circuit were burned up. The...

Does your transistor tester also have capacitor testing capability?