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 Post subject: Admiral 5B1 Audio Low
PostPosted: Sep Wed 15, 2021 5:12 am 
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Joined: Aug Thu 09, 2018 3:00 am
Posts: 28
Hi all, just acquired and Admiral 5B1 with very low audio. replaces all caps , and checked resistors . Tubes are good. Looks like the speaker is not original. It has an output transformer mounted on it. primary reads @ 270 ohms, secondary reads about 3 ohms. Does this seem right? Primary seems a bit high. Could this account for my low audio? Anyone know the proper resistance readings? Thank you.


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 Post subject: Re: Admiral 5B1 Audio Low
PostPosted: Sep Wed 15, 2021 7:40 am 
Member

Joined: Jan Mon 16, 2012 4:15 pm
Posts: 8042
Location: Near Brandon, Iowa
Those readings are about what is expected; especially on the secondary side if you left it connected to the voice coil when you measured its resistance.

What is the B+ voltage? Have you aligned the set? What is your basis for saying that the "tubes are good"?

Please clarify what you mean by "replaced all the caps"? If this is literally true your radio will need to be aligned before it will perform properly (there are fixed mica caps in the RF and IF sections that should not be replaced when "recapping" a set).


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 Post subject: Re: Admiral 5B1 Audio Low
PostPosted: Sep Thu 16, 2021 5:09 pm 
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Joined: Aug Thu 09, 2018 3:00 am
Posts: 28
B+ voltage is @106VDC , measured at the electrolytics. I did not replace the mica caps, just the electrolytics and wax/paper caps. tried alignment, not much help. Tubes checked on a tube tester.


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 Post subject: Re: Admiral 5B1 Audio Low
PostPosted: Sep Thu 16, 2021 5:36 pm 
Member

Joined: Jan Mon 16, 2012 4:15 pm
Posts: 8042
Location: Near Brandon, Iowa
Right now it's a tossup as to whether the low volume is cause by a weak audio stage, or a poorly-working RF stage.
To get a better handle on where to look for the problem, you might inject an external audio signal into the grid of the first audio amp tube and see if you get decent volume out of the speaker.


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 Post subject: Re: Admiral 5B1 Audio Low
PostPosted: Sep Thu 16, 2021 5:38 pm 
New Member

Joined: Sep Thu 16, 2021 3:48 pm
Posts: 8
Location: missouri usa
have you tried swapping the tubes if you have extras? and does it use a 50C5 for the output

_________________
"let it make some sound"


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 Post subject: Re: Admiral 5B1 Audio Low
PostPosted: Sep Fri 17, 2021 1:46 am 
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Joined: Aug Thu 09, 2018 3:00 am
Posts: 28
Tried swapping tubes first. No change. 50L6 output tube


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 Post subject: Re: Admiral 5B1 Audio Low
PostPosted: Sep Fri 17, 2021 4:38 am 
Member

Joined: Aug Thu 09, 2018 3:00 am
Posts: 28
problem fixed ! Dummy me. This is from a radio/phono combo unit. 2 wires on the plug need to be jumpered for audio. The wires go to a radio/phono switch. I jumpered them and now have good audio. Thanks for all the ideas ! Now is someone could lead me in the right direction to find a dial scale for this radio, that would be great. Jim


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 Post subject: Re: Admiral 5B1 Audio Low
PostPosted: Sep Fri 17, 2021 5:58 am 
Member

Joined: Aug Thu 09, 2018 3:00 am
Posts: 28
Correction, not the dial scale, but the piece of background plastic that the pointer rides on. Looks like they can be produced. White or cream colored plastic. p/n 22B7 . Anyone have one?


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