[dconant]

I have been doing some more checking on the chassis. I have found one of the chokes is not measuring as it is shown in the schematic. Part 120 is supposed to be 400 ohms but it is reading 3K. The part may not be original to the chassis as I see some sloppy soldering and cut wires that must have gone to the original one. I assume the 3K is going to cause a problem. Do I need to locate another one?

I also noticed ECaps 126 and 127 are 8MF wired in parallel. Can I just use one 16MF instead?

[Greg]

Mine was bad too.
I got a replacement off of ebay, a 32-7056N (not sure what the N means).
That's not the "same" part as the original is 32-7491.
However, I believe that if you look in parts catalogs for the specs you'll find they are the same.
The only "difference" is that leads exit differently.
One has both leads on one side and the other has them on opposite sides. (Don't recall which is which).

If you order one, be careful as I suspect it could be bad too.

I see two 32-7056 listed. One seems $$ and the other $$$.

[dconant]

Hi Greg, Thanks for the info. I might be better off getting a new Hammond one. They are both the one on top of the chassis. I need the 32-7491 filter and it mounts under the chassis.

Dan

[Greg]

Yes on the caps... 1x16 will be just fine. In either case just make sure the voltage rating is >= to the specified.
I just paralleled some 630V film caps for some of the other e-caps in mine.

I used a 32-7056 in place of the 32-7491. It fits in the place of the original.

[dconant]

Thanks Greg I was pretty sure it would be ok but you never know what the engineers are thinking.

Dan

[dconant]

Hello, I need to replace one of the grid wires coming out of the selector mechanism. I see 4 screws on the bottom of the cans, two on each side. If I take those screws out will I gain access to replace the grid wire? I'm worried there may be nuts under the screws.

Anyone know why the .004 paper cap (#74) is a 1000 volt cap. It is attached to the volume control.

Thanks,
Dan

[MrFixr55]

Hi Dan,
Chances are that the 1000V cap is what they had available.

The cap in question couples the detector to the volume control. There is no B+ on that cap, and likely no more than about -20V or so AVC voltage and less than about -3V grid bias for the 1st audio amp. Most replacement mylar caps from suppliers to the hobby are rated for about 630V max. Non-electrolytic caps are rated for a maximum voltage. Fore a radio whose maximum B+ voltage is 250V, a 630V cap provides more protection from dielectric breakdown than a 400V cap.

However, electrolytics are rated in working voltage, so it is not good to use a 500 WV (Working Volt) cap in an AA5 radio whose rectifier generates about 150VDC. Maximum voltage tolerated by an electrolytic cap is not much higher than the working voltage, so take no-load voltage into consideration when picking electrolytic caps.

[morzh]

Exactly. It's just that they had limited variety of caps; it was much cheaper. What does it matter if the cap costs you pennies? so you put a 1kV cap where 50V would suffice, who cares.
Same what I do: I keep most of my axial film caps rated at 630VDC. I could have that one variety and buy in bulk.

[dconant]

MrFixer55 why do you say putting a 500wv ECap in an AA5 radio is not good? Not sure but I may have done so.

Dan

[morzh]

I did not read anything like this im MrFixr's post.
Any AA5 radio would have its B+ under 200V, so 500V electrolytic is just fine there.
Not just that, B+ in transformer sets is more like 300-plus Volts, and before the filter it is closer to 350-370VV and briefly shoots up to 420-450V before the load kicks in, and they used 450V caps originally (I use 500V). And even this is just fine.