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 Post subject: Re: 1964? Panasonic T-81H AM/FM/SW -- latest arrival (nice)
PostPosted: Jan Mon 09, 2017 12:06 am 
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Joined: Aug Wed 26, 2009 1:50 am
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Location: Mount Pleasant UT 84647 (from Coventry, UK)
Excellent news.

Colin


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 Post subject: Re: 1964? Panasonic T-81H AM/FM/SW -- latest arrival (nice)
PostPosted: Jan Mon 09, 2017 2:15 am 
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Joined: May Wed 01, 2013 10:05 pm
Posts: 873
Location: British Columbia, CANADA
I knew you wouldn't give up that easily John, you can't stop now.

Today I also found my bias regulator is shorted in both directions (34 ohms) and an audio driver transistor is open.
Using my signal tracer I'm getting good strong audio just before the driver on both AM and FM.

Looks like anything close to a 2SB173 will work, I tried a few subs already, but not sure what to do about the "bias reg"


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 Post subject: Re: 1964? Panasonic T-81H AM/FM/SW -- latest arrival (nice)
PostPosted: Jan Mon 09, 2017 2:22 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4295
Location: Indianapolis, IN
Thanks Guys---was sure relieved, believe me !

Rocco---I am wondering about the bias regulator also as I don't know how many of their radios uses that specific one and what can be used as a sub. Am already searching for the matched pair outputs and have found a couple of their cheaper sets that use them. Stay tuned as I'll post what I find. Glad your problem was only in the audio !

John


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 Post subject: Re: 1964? Panasonic T-81H AM/FM/SW -- latest arrival (nice)
PostPosted: Jan Mon 09, 2017 4:02 am 
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Joined: Jun Tue 21, 2011 8:27 pm
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Location: Virginia
Mitch


Last edited by PBPP on Jan Tue 10, 2017 7:43 am, edited 1 time in total.

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 Post subject: Re: 1964? Panasonic T-81H AM/FM/SW -- latest arrival (nice)
PostPosted: Jan Mon 09, 2017 7:32 pm 
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Joined: May Wed 01, 2013 10:05 pm
Posts: 873
Location: British Columbia, CANADA
I checked my MA23 again and it does act like a diode so I think it's ok.
It also drops in resistance when heated.

The way it's wired in the circuit I'm thinking it's acting like a thermistor that I've seen in other audio stages.

An MA23 also refers to an NTE109 equivalent (fast switching germanium diode)
there's a data sheet on this page.

http://www.weisd.com/test/GenericParts_ ... id1=MA23(B)


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 Post subject: Re: 1964? Panasonic T-81H AM/FM/SW -- latest arrival (nice)
PostPosted: Jan Tue 10, 2017 3:18 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4295
Location: Indianapolis, IN
Thanks Mitch---responded in more detail via e-mail.

And thanks Rocco for your info---so it doesn't conduct both directions as you mentioned earlier ? Maybe then, the driver will get it going !

John


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 Post subject: Re: 1964? Panasonic T-81H AM/FM/SW -- latest arrival (nice)
PostPosted: Jan Sun 15, 2017 11:24 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4295
Location: Indianapolis, IN
Went ahead and cleaned all the "cosmetics" & pieces this weekend and put all away until I can find the transistors needed...

Pics below...

John


Attachments:
ARF T81H PRTS CLN.jpg
ARF T81H PRTS CLN.jpg [ 192.17 KiB | Viewed 26 times ]
ARF T81H CAB PRTS CLN INS.jpg
ARF T81H CAB PRTS CLN INS.jpg [ 191.36 KiB | Viewed 26 times ]
ARF T81H CAB PRTS CLN OUT.jpg
ARF T81H CAB PRTS CLN OUT.jpg [ 236.3 KiB | Viewed 26 times ]
ARF T81H SPKR BK CLN.jpg
ARF T81H SPKR BK CLN.jpg [ 227.04 KiB | Viewed 26 times ]
ARF T81H SPKR FRT CLN.jpg
ARF T81H SPKR FRT CLN.jpg [ 202.46 KiB | Viewed 26 times ]
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