Batboard

I have many schematics on the Astron Power Supplies but no part names. I recently fixed a 20 A power supply by replacing a small block that had 4 connectors on it. It was a small block 1"X1" molded with plastic and dialectric white compount on it with 1 screw holding it to the chassis. I took it off another non-working power supply. Trying to find out what part this is? Retifier block? And how to get another one.

From your description, it sounds like a bridge rectifier module. To confirm that's what it is, you should be able to check the diodes inside by doing a front-to-back resistance check, or, if your DVM has a diode position, that will work too.

A good diode will show 0,6V forward drop. A bad one, 0V. Similarly, low resistance in the forward direction, high resistance reversed.

Put the leads on the tabs next to each other, one pair at a time, and go around the block, as it were.

An R20 supply is not 20A continuous, but intermittent duty. You could use a 25A, 100V PIV bridge just fine, provided it has a center screw hole of the right size.

The white stuff on the back is silicone grease, and the idea is to make a good thermal junction with a heatsink or large hunk of metal in order to dissipate the power dissipated by each diode. (E times I, where E is 0.6V and I is whatever the RMS current flow happens to be and you have 4 of them)

Lee
60HzEE

The bridge rectifier failing is probably the most common problem in the Astrons. Usually one or more of the diodes shorts out, causing the fuse to blow.

None of the ones I've replaced had been running anywhere near their ratings, so the cause of failure is most likely a surge on the power line.

I always replace them with ones that have a bit better ratings, not only current, but also voltage, for the RS-20 I'd use a 35A/400V one. The size is the same as the 25A/100V, and the difference in price is about 50 cents.

As for where to get them, try Mouser.com, look for the Rectron brand, I believe those are the ones I've been using.

i find the IC (comparator) is the most common failure.
13.8 volts with no load. radios recieve fine but then tx and volts drop way down.

Thank you All. Your info was a big help. It was blowing fuses until the Bridge Rectifier was replaced. Now I know what the part is and what it does and where to get them. Smiles to you

If you need some good cheap rectifiers of that nature go to the All Electronics website or Surplus Sales of Nebraska. They both carry them in 20, 35, 50, and sometimes they even have 75 and 100+ amp ones as well.

Thats where i get them from.

Hello :
I have a RM50 Astron that id like to replace one of the caps in .
Its a 42000 MFD - Mallory brand at 25 vdc / surge 30 vdc.
I have looked for this cap on digikey and eci along with a google search but didnt find anyone that had it.
Any chance someone here would have one or know where i could get one ?
It has the two tapped screws that the electronics astron bd attached to but i could use the flying lead type if it wasnt teribly huge.
Limited a bit on room in the case.
Anyone by chance know the phone number or webb site to astron ?
Thanks Satelite

Mallory # 473U025V4C 47000uF @ 25 volts

Cornell Doublier # DCMC473U025BA2B 47000 uF @ 25 volts