Howard 482

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Howard 482

Post by Wildcat445 on Sun Aug 23, 2015 7:39 pm

I am trying to get this FM tuner to work.  This is one of those tuners made to run thru the phono input on a radio chassis.  The circuit diagram is in Riders 19, Howard page 2.  

There are five pages of service information, but no element voltages listed that I can see.  I need to run the voltages in this chassis.  I have no output from this tuner at all.  The only voltage I see listed is for the cathode of the rectifier, listed at 145VDC.  I have over 160 volts there, measured with my VTVM.  That seems a tad high, so maybe something is not conducting current?  I only have 20 volts DC on the plate of the 6J5 audio tube, and that does not seem to be enough to me.  The chassis has been recapped and the filter cap can has been re-stuffed. There is a 330 ohm, 2 watt resistor off the cathode of the 6X5 that checks good.  There is a 66k resistor from the first filter cap to the second one and it checks 44K only.  There is a 220K ohm resistor in the plate circuit of the 6J5 and it tests 242+K.  These will be replaced, but they don't seem enough off to kill B+ to the 6J5.  I'm not even sure that the 6J5 is the problem, but that is where I would like to start.  Has anybody messed with one of these or would be willing to bail me out?  Thanks.

WC


Last edited by Wildcat445 on Mon Aug 24, 2015 5:00 pm; edited 1 time in total

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Re: Howard 482

Post by mr_ed01 on Sun Aug 23, 2015 9:08 pm

It is listed in Sams set 48, folder 12. Don't have it in my collection, maybe someone else does.

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Re: Howard 482

Post by Wildcat445 on Sun Aug 23, 2015 9:23 pm

Thanks for looking.

WC

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Re: Howard 482

Post by Guest on Sun Aug 23, 2015 9:51 pm

I will look in the shop tomorrow.

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Re: Howard 482

Post by Wildcat445 on Sun Aug 23, 2015 11:26 pm

Thanks, Mez.

WC

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Re: Howard 482

Post by Wildcat445 on Mon Aug 24, 2015 5:05 pm

First off, the set I have is a 482, not an "A".  It has the 12AT7 tube instead of a 6J6.  

I found that the oscillator is running, evidenced by negative voltage on the grid of the 6BA6 converter.  Next, I determined that I have at least a working audio section.  I placed my finger on the center terminal of the volume control and got a growl in my signal tracer.  Not a really healthy growl, but it tells me that all my trouble is not in the 6J5 circuit.  This section is weak, but I moved on.  I find I have audio up to the plate of the 2nd IF amplifier, a 6BA6.  Next is to find out where the signal dies between there and the volume control.  The 6AL5 FM detector and its circuitry are next being up for test. Having less than 20 VDC on the plate of that 6J5 is of concern. This is the first totally comatose FM receiver I believe I have ever messed with.

WC

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Re: Howard 482

Post by Guest on Mon Aug 24, 2015 5:50 pm

I do not have a copy of this schematic.

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Re: Howard 482

Post by Doug Burskey on Mon Aug 24, 2015 8:35 pm

I think that 482 FM tuner was only thing Howard Radio made in any large numbers. I have one and have seen several of them.

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Re: Howard 482

Post by Wildcat445 on Mon Aug 24, 2015 10:45 pm

Mez, I appreciate your looking for the schematic. Doug, this is the first FM converter I have ever had. This is one of the nastiest ones I have seen, but the price was right. I've had it for some time, so I figured I needed to get it going. After I get it to work I can make it look better. If it won't work, it goes in the parts bin.

WC

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Re: Howard 482

Post by Wildcat445 on Sat Aug 29, 2015 10:58 am

I'm going to need more information than I currently have in order to troubleshoot this chassis. The problem seems to be in the discriminator circuit. Specifically, between the plate of the last IF tube and the volume control. There are ceramic caps, the 6AL5 (subbed, with no difference) and the discriminator transformer. It appears to have continuity. I can't pass a 400 cycle audio signal from the 6AL5 to the volume control. Perhaps spending a year or so on the end of the bench will provide additional insight?

WC

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Re: Howard 482

Post by Dr. Radio on Sat Aug 29, 2015 9:18 pm

Ceramic caps garbage? Might be if this is the only stumbling block left in the path...
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Re: Howard 482

Post by Wildcat445 on Sun Aug 30, 2015 12:24 am

The main problem appears to be really horrible service information. I need voltage specs. I can guess, but I have tried that and that is not working out well. A ceramic cap is my suspicion, but ceramics don't go bad, right? I'm not certain that my ONLY problem is between the 6BA6 and the volume control, just the first problem I've found.

WC

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Re: Howard 482

Post by Dr. Radio on Wed Sep 02, 2015 8:08 pm

Ceramic caps can go bad.

One minute they're headed off to school, the next minute they're hanging around the street corner smoking with their hoodlum friends.


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Any updates on this project?
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Re: Howard 482

Post by Wildcat445 on Wed Sep 02, 2015 11:47 pm

I haven't had time to get back on this.

WC

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Re: Howard 482

Post by Bill Cahill on Thu Sep 03, 2015 9:58 am

I've seen many bad ceramic caps. In the 60's GE was using a ceramic paper cap across the BW tv yokes. Boy, do they go Bang!!
Elmenco used to make the best. They're all junk, now.

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Re: Howard 482

Post by Wildcat445 on Thu Sep 03, 2015 11:08 am

Perhaps I can get some time in the next couple days to get back on this. I appreciate your input. I'll take a closer look at those ceramic caps for sure.

WC

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Re: Howard 482

Post by Doug Burskey on Thu Sep 03, 2015 12:55 pm

The mica caps can go bad as well. In all the radios I have restored I have found 2.

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