Interesting.
I thought that notes about the back of a device being connected to a pin meant that you had to be careful when mounting it to a heatsink... particularly if you were mounting multiple devices on that heatsink. It never occurred to me that it was intended to be the first means to connect the device to the circuit -- that's what the pin is for, right?
If I remember correctly some builds have omitted the heatsinks and worked.
From the pictures I would have guessed that you would have had a shorting problem on the negative leg where the heatsink has displaced R32.
I thought that notes about the back of a device being connected to a pin meant that you had to be careful when mounting it to a heatsink... particularly if you were mounting multiple devices on that heatsink. It never occurred to me that it was intended to be the first means to connect the device to the circuit -- that's what the pin is for, right?
If I remember correctly some builds have omitted the heatsinks and worked.
From the pictures I would have guessed that you would have had a shorting problem on the negative leg where the heatsink has displaced R32.
The heatsinks are not connected to ground. The circuit will work with no insulators.
Are the fins touching anything by chance?
Are the fins touching anything by chance?
Should I leave it as is or do some more inspection of the boards?
The second board powered up fine without the insulator and passed the DBT test.
The second board powered up fine without the insulator and passed the DBT test.
You could remove the heatsinks for a little while, or attach something smaller as mhenschel suggests.
Yep. I had an extra pair of smaller heat sinks. I swapped it out on 7824 on one board and it powered on fine. Going to swap the heat sink on the other board and confirm that fixes the issue.
I think what was happening was the heatsink in contact with the capacitor was creating a short. The body of an electrolytic capacitor has voltage. You can measure it with a volt meter from top of capacitor to V+ and top of capacitor to ground. I just did that on one of my power supplies.
Even though the regulator was separated from the heatsink with an insulating layer, the screw fastening the regulator to the heatsink still contacted both the heatsink and the metal ground tab of the regulator. Therefore the heatsink was grounded.
Edit
I just noticed shoulder washers on the screws. So perhaps the isolation was not perfect?
Even though the regulator was separated from the heatsink with an insulating layer, the screw fastening the regulator to the heatsink still contacted both the heatsink and the metal ground tab of the regulator. Therefore the heatsink was grounded.
Edit
I just noticed shoulder washers on the screws. So perhaps the isolation was not perfect?
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I replaced the two heatsinks on the 7824s and we are now passing the dim bulb test with both boards and insulators between the 7824s and sinks. I only had two heatsinks so I will be getting new ones for the 7924s. I’m off to work and will try to find matching sinks locally.
I also think the plastic inserts I had were junk and did not fit well into the regulator. After replacing one sink on one board I was having issues but realized the plastic washer did not do it’s job and the regulator was not lined up correctly.
Thanks for all the help. Once I finish the phono I’ll post pics.
I also think the plastic inserts I had were junk and did not fit well into the regulator. After replacing one sink on one board I was having issues but realized the plastic washer did not do it’s job and the regulator was not lined up correctly.
Thanks for all the help. Once I finish the phono I’ll post pics.
I ended up purchasing two more heatsinks from Mouser to match the other two I just added. Luckily Mouser ships from Texas so I should get them tomorrow.
Ok.. new issue coming up. I realized that my DBT is also being set off by my Pad ground wire that runs from my grounding star and grounding lugging the center of the boards above C12.
If I unhook these wires I have no issues.
If I unhook these wires I have no issues.
Do the common ground wires need to be hooked up? For some reason I am getting -27V on the middle ground point if I put my negative probe on the star ground and positive probe on that center ground pad.
OK. Disregard all that... I discovered my issue and it was probably what was causing the problem the whole time.
My DIY umbilical power cord had a short in it. While testing voltages I noticed I was getting -24V at the chassis. So I tested the outside of the umbilical adapter and sure enough it was giving off -24V. I took it apart and found a tiny rip where the wire had been exposed and was touching the outer metal of the adapter.
I took extra precaution re-soldering, adding just the right amount of heatshrink, and making sure not to force the wires through the adapter.
Another test with the common grounds connected and we are now good! I am allowing the soldering gun to heat up so I can run my rca wires...
My DIY umbilical power cord had a short in it. While testing voltages I noticed I was getting -24V at the chassis. So I tested the outside of the umbilical adapter and sure enough it was giving off -24V. I took it apart and found a tiny rip where the wire had been exposed and was touching the outer metal of the adapter.
I took extra precaution re-soldering, adding just the right amount of heatshrink, and making sure not to force the wires through the adapter.
Another test with the common grounds connected and we are now good! I am allowing the soldering gun to heat up so I can run my rca wires...
I ordered them and they should arrive tomorrow.
Phono is hooked up and it works!
As for loading resistor, if I leave it open does the cartridge automatically see 47k? And anything I add in parallel gets me a new value?
Phono is hooked up and it works!
As for loading resistor, if I leave it open does the cartridge automatically see 47k? And anything I add in parallel gets me a new value?