Regency base station-120 volt side problem

[press1280]

Hi all, working on an old Regency 23 channel SSB base. The 13.8 volt DC side works, the 120 volt side doesn't.

The 120 volt side has a transformer with a small circuit board which is isolated from the rest of the components. The transformer is putting out around 18 VAC, but there is no voltage where the power is supposed to leave the board and tie into the rest of the radio. There are 2 capacitors on this board, I replaced the small one (220 uf) and still didn't get anything. The larger one (2200 uf) apparently has 3 terminals (A, B (dummy load), and negative. I checked capacitance across each terminal and got absolutely nothing. I'm not familiar with these capacitors and just wanted to see if there was some other way I should test or whether it's dunzo?
And I'm assuming the 120 VAC side board is just stepping down the voltage and then acts as a rectifier?

 

[prcguy]

There would be some diodes to rectify the 18VAC out of the transformer into DC before the filter capacitors. It could be two diodes right off the transformer or four individual diodes in a bridge or a square plastic housing. Then there would be a regulator circuit to supply 12 to 14 volts to the rest of the radio. Find the 18VAC again then look for any rectifiers and test for DC voltage. You should see over 20 volts DC on the big 2200uf filter capacitor. If its not there It could be the rectifiers are bad or the capacitor has gone bad and is shorted. Or a bunch of other possibilities.

 

[press1280]

There would be some diodes to rectify the 18VAC out of the transformer into DC before the filter capacitors. It could be two diodes right off the transformer or four individual diodes in a bridge or a square plastic housing. Then there would be a regulator circuit to supply 12 to 14 volts to the rest of the radio. Find the 18VAC again then look for any rectifiers and test for DC voltage. You should see over 20 volts DC on the big 2200uf filter capacitor. If its not there It could be the rectifiers are bad or the capacitor has gone bad and is shorted. Or a bunch of other possibilities.

I've removed the capacitor from the board. None of the terminals are showing any capacitance. Is it shot?

 

[prcguy]

It could be. What are you testing it with? What model is the radio?

I've removed the capacitor from the board. None of the terminals are showing any capacitance. Is it shot?

 

[press1280]

Multimeter. Model is CR-123B. Couldn't find any info for that model on CB tricks

 

[prcguy]

Does the multimeter test capacitors? I see a Youtube video of someone working on a CR-123B and they showed the little regulator board with the capacitors you mention. There are four diodes in a bridge configuration that would then feed the big capacitor and when working you should see over 20 volts on the capacitor as I mentioned before. It looks like it might be a low current regulator maybe using a zener diode and a pass transistor that is not heatsinked, so it may not feed 12v to the entire radio.

 

[buddrousa]

I had forgotten radio prices in the mid 70's $399 price in 1975.
I remember my Tram D201, T Berry Model T, and a few others I had I was lucky as I bought all my gear at cost plus 10%.

 

[press1280]

Does the multimeter test capacitors? I see a Youtube video of someone working on a CR-123B and they showed the little regulator board with the capacitors you mention. There are four diodes in a bridge configuration that would then feed the big capacitor and when working you should see over 20 volts on the capacitor as I mentioned before. It looks like it might be a low current regulator maybe using a zener diode and a pass transistor that is not heatsinked, so it may not feed 12v to the entire radio.

Yes, it tests capacitors (at least the 2 terminal type). I tested the small capacitor and came up slightly higher than its rating (250 uf to 220 uf). I saw a few youtube videos on it. There's one video where I can see someone removed that large capacitor and replaced with 2 wires and what looks like a smaller capacitor, but I could only see it for a quick second or two.
I was looking around for a replacement but it seems like these type of capacitors may no longer be made?

 

[buddrousa]

You best bet may be to use a 10 or 20 amp ASTRON POWER SUPPLY unless you want to restore it to vintage state and see what it brings.

 

[press1280]

You best bet may be to use a 10 or 20 amp ASTRON POWER SUPPLY unless you want to restore it to vintage state and see what it brings.

I have a micronta power supply. I'm not trying to restore it per se but I'd like to get the 120 v side working since it is a base station after all.

 

[prcguy]

Every capacitor in that radio is common and available today, although they might be a little smaller due to leaps in technology.

Yes, it tests capacitors (at least the 2 terminal type). I tested the small capacitor and came up slightly higher than its rating (250 uf to 220 uf). I saw a few youtube videos on it. There's one video where I can see someone removed that large capacitor and replaced with 2 wires and what looks like a smaller capacitor, but I could only see it for a quick second or two.
I was looking around for a replacement but it seems like these type of capacitors may no longer be made?

 

[press1280]

Every capacitor in that radio is common and available today, although they might be a little smaller due to leaps in technology.

Any idea what these are called??

 

[prcguy]

It would be a radial lead electrolytic. I'm sure the large capacitor on the little circuit board would be in the 2,200uf range and at least 25 volt rated. Here is an ad for something similar. 4PCS 2200uF 25V Electrolytic Capacitors 25V 2200uF | eBay

Any idea what these are called??

 

[press1280]

It would be a radial lead electrolytic. I'm sure the large capacitor on the little circuit board would be in the 2,200uf range and at least 25 volt rated. Here is an ad for something similar. 4PCS 2200uF 25V Electrolytic Capacitors 25V 2200uF | eBay

Those are 2 terminals, mine is 3. Perhaps this would work just connecting to the + and - terminals only?

 

[merlin]

IF that 120 VAC is there, then look at the secondary connections, 2 0r 3 depending half or full wave bridge. That should be about 20 VAC center to either end for half wave or end to end for full.
That will tell you if the transformer is working. Next in line is the bridge/ filter cap circuit. Now we are into DC volts if that is working. + DC voltage on the + side of the filter caps. Nothing there means something mentioned is not satisfied.
Fuse blown in the primary circuit ? Bad caps won't change this.
Unlike today's switching supplies that eat electrolytics, Most filter caps I see are good 40 years later. The job of these caps is to filter the ripple from the bridge and may even include a series inductor or resistor. Everything good, you now have your hi DC that goes to any regulators.
3 conductor radial caps are often dual electrolytics with different values, usually indicated by a 'U' or 'V' at the contact or simply an unused pin.

 

[press1280]

I've already verified the transformer (and primary voltage in) are working. The question at the moment is since I've already removed the 1 radial cap, and it shows no capacitance on my multimeter between any 2 terminals, is it bad? (it does show resistance if that matters)
My understanding is the caps would be more likely to fail than a diode or resistor.

 

[press1280]

See attached

 

[prcguy]

You should show rated capacitance between A and ground and an Ohm meter should show a brief short then go up to several K ohms as the capacitor charges.

I've already verified the transformer (and primary voltage in) are working. The question at the moment is since I've already removed the 1 radial cap, and it shows no capacitance on my multimeter between any 2 terminals, is it bad? (it does show resistance if that matters)
My understanding is the caps would be more likely to fail than a diode or resistor.

 

[WA0CBW]

That is a standard two terminal capacitor with a third non used terminal. This "dummy" terminal was used to stabilize mounting the capacitor to the board.
Bill

 

[prcguy]

If the capacitor is actually bad the type of capacitor in the Ebay link I provided will work just fine. You just need to put the + and - leads to the right pads.