Regency base station-120 volt side problem

[prcguy]

You mentioned one of the big diodes is cracked and if so it would be open. I would unsolder one end of each diode and check with your meter to see if the rest are good.

With one diode open you would only charge the filter cap during one half the AC cycle, it should charge up to something but will not produce much under load. I suspect other diodes are bad and no DC is getting to the big cap. Or the cap shorted and that's why the diode(s) are bad.

Otherwise 20VAC sounds ok off the transformer secondary leads. A little high in my opinion which will cause the regulator to dissipate more heat, but ok.

Put the transformer back in. I'm reading 20 VAC just on one side of the bottom right diode, while the diode 2 spots down is reading 20 volts on the opposite side of the diode. No voltage to the capacitor, and nothing on the other 2 diodes.

 

[press1280]

You mentioned one of the big diodes is cracked and if so it would be open. I would unsolder one end of each diode and check with your meter to see if the rest are good.

With one diode open you would only charge the filter cap during one half the AC cycle, it should charge up to something but will not produce much under load. I suspect other diodes are bad and no DC is getting to the big cap. Or the cap shorted and that's why the diode(s) are bad.

Otherwise 20VAC sounds ok off the transformer secondary leads. A little high in my opinion which will cause the regulator to dissipate more heat, but ok.

It's the bottom right diode that's cracked with voltage in, nothing out.

 

[prcguy]

I would just replace all four diodes and the capacitor at this point and get ready to do more testing once they are powered up. Here are some diodes that should work fine and are probably an upgrade over stock. You can probably get away with 3A 50 or 100V.

GS BY500-200-E3/54 DO-201AD 200V 5A General Purpose Diode New Quantity-5 | eBay

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It's the bottom right diode that's cracked with voltage in, nothing out.

 

[press1280]

I assume these are “rectifier” diodes?

 

[krokus]

I assume these are “rectifier” diodes?

Yes, they are.

 

[press1280]

So it appears the diodes did the trick. It actually powered up when I had only 2 of them in place.

Once question though is that I can't directly solder them to the board. The leads on these diodes are too thick. I just took some skinny capacitor wires and just rigged them up for the test. Any recommendation for a more permanent connection?

 

[prcguy]

You can sometimes drill out the hole a little larger for the new lead or bend a tiny foot on the end of the lead and solder it to the foil side of the board if the solder pads will accommodate that.

So it appears the diodes did the trick. It actually powered up when I had only 2 of them in place.

Once question though is that I can't directly solder them to the board. The leads on these diodes are too thick. I just took some skinny capacitor wires and just rigged them up for the test. Any recommendation for a more permanent connection?

 

[press1280]

You can sometimes drill out the hole a little larger for the new lead or bend a tiny foot on the end of the lead and solder it to the foil side of the board if the solder pads will accommodate that.

I'll try to open up the holes a little bit and do it from the top. Thanks!

 

[press1280]

Replaced the 4 diodes and capacitor and it works!
All good.

 

[prcguy]

Congratulations! I have a CPI CP-300 I would like you to fix....

Replaced the 4 diodes and capacitor and it works!
All good.

 

[press1280]

Oh boy. Never seen one of those before. Looks nice!