[rocketeer]

I've started working on my 40-150 and found this set of electrolytics under the chassis. The parts list and schematic call for one 16mfd - 200v, and one 12mfd - 350v, both residing in a topmount can. However, one side is disconnected and replaced with a pair of 10mfd - 500v caps and the other side has all the pins soldered together. I figured it was a hack job until I searched the internet for info on repairing a 40-150 and saw two other chassis with virtually the identical setup underneath. What does piggy-backing a pair of lytics like this accomplish?

Schematic here:
http://www.nostalgiaair.org/resources/331/M0013331.htm

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Larry

[Texasrocker]

Thanks for providing the schematic link for the radio you are servicing. I took a quick look at it. Without going into detail of how electrolytic caps work in "parallel" and (opposite) "series" connections, just do this... Replace both,.. the 2 "piggybacked electrolytics" in your set with 1 ( 20 uf@ 350 volts). Replace the other with the same value. you will be good. In short to answer your question, those 2 caps installed "piggybacked" before in "parrallel" were to meet the required voltage ratings required when they were installed previously. The tech used what he had at the time in his shop. Observe polarity when you install any new electrolytics, and Best of luck with all your restorations!

[rocketeer]

Thanks, I know what to replace, I was asking why this appears to be fairly common since I have now seen three instances of this identical repair using a pair of parallel caps on a 40-150. I was also commenting on all the pins being soldered together on the original cap with one half of it still connected in circuit. I probably could have worded the question better.

Larry

[Arran]

Thanks for providing the schematic link for the radio you are servicing. I took a quick look at it. Without going into detail of how electrolytic caps work in "parallel" and (opposite) "series" connections, just do this... Replace both,.. the 2 "piggybacked electrolytics" in your set with 1 ( 20 uf@ 350 volts). Replace the other with the same value. you will be good. In short to answer your question, those 2 caps installed "piggybacked" before in "parrallel" were to meet the required voltage ratings required when they were installed previously. The tech used what he had at the time in his shop. Observe polarity when you install any new electrolytics, and Best of luck with all your restorations!

Sorry but I beg to differ, the connected them in parallel to increase the capacity not the voltage rating, they put two 10 mf caps in parallel to act as a 20 mf filter. If they had connected them in series they would have increased the voltage rating to 1000 vdc since they were both 500 volt rated caps but halfed the capacity to 5 mfd.
Regards
Arran

[gvel]

It looks like this may be a hack job, Larry. The replacement side was done correctly, but now, it seems to me, the can has both sections tied together, and it's still in circuit.

With the pins tied this way, the can has one section, at 28uF. The two sections are connected in parallel.

On the other hand, are you sure this is the original filter can? If not, the tech may have had a dual section cap, that would accommodate this application, when he tied the two sections together. If that is the case, it was a correct fix.

Nonetheless, you know where to go, from here.

[rocketeer]

The can is actually a 3 section can: 10mfd - 350v, 15mfd - 350v, 20mfd - 25v. The bottom is buggered so I can't tell what pins are actually connected but suspect it's the two 350v's. At any rate, it all gets replaced.

Larry

[Texasrocker]

You are absolutely correct Arran. I misread the values on those piggybacked caps. Didn't have my reader glasses on when I looked at the photo. I was paying more attention to the schematic. Thanks! good catch there!

[Radioroslyn]

This getin' old stuff is for the birds!!
Terry

[rocketeer]

I finally got this thing up and running last night. It took quite a while before I started to get at least noise through the speaker. That's when I discovered both the On/Off/Tone control and the Volume control had issues. As it turned out both were shot. Thanks to a fellow member on ARF I was able to get a good pair of used controls. I installed them and with just a bit of tinkering last night she finally plays.

This was a rough one. The variable capacitor was corroded and initially frozen as were the idler wheels for the dial string. A couple of the loktal tubes were unreadable and as a result were switched in their sockets. One octal socket was cracked across. None of the octal socket pin sockets made contact and had to be squeezed with a needlenose pliers. The electrolytics were miss-wired. There was a small black "jelly bean" where a mica was spec'd. I have no idea what that soft gooey glob was but it's gone now. The push button mechanisim was messed up and had several wires disconnected. The dial scale was so dirty some numbers weren't visible and the dial scale reflector was filthy. And,,,, there was all that wonderful rubber wiring. But,,, she's all better now!

Now I have to wait for Spring to do the cabinet.

Larry

[gvel]

Great work Larry! Sounds like you really had a basket case!

[rocketeer]

I connected up the antennas (6 antenna wires for one radio?) and aligned this baby. Someone had cranked down the second IF and when I unwound it did she ever perk up, wow! Amazing power for a 7 tube tabletop! I think once the cabinet is done this just might become a keeper for the bedroom.

Larry