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8th Nov 2012, 7:55 pm
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#1 |
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Hexode
Join Date: Feb 2011
Location: Gloucestershire, UK.
Posts: 376
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Bush TR82
Stumped here:
I've got the version with the AF117's... each one appear OK by test (and substitution with AF239) but I've got very very low and very distorted audio. The radio's pulling about 20mA from the battery. I can see the audio on the 470KHz IF at TR3, and putting a finger on the base of TR4 (OC71) gives a nice healthy buzz from the speaker... I can't find the detector, X1, but I've only got the diagram for the version with all OC's. Is it inside the can between TR3 and 4? Does that can come apart? How can such a simple thing give me so much grief 
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8th Nov 2012, 8:31 pm
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#2 |
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Pentode
Join Date: Oct 2005
Location: Harlow, Essex, UK.
Posts: 162
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Re: Bush TR82
The detector diode is inside the IFT3 can between TR3 and TR4.
Try changing C19 (8uF) just above VT4 (TR4) and C20 (0.04uF) on the volume pot. |
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8th Nov 2012, 10:22 pm
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#3 | |
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Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,580
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Re: Bush TR82
Quote:
....and it's common for it to fail. Had it several times with these. Remove the can and fit an OA91. Rich.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
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9th Nov 2012, 3:06 am
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#4 |
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Retired Dormant Member
Join Date: Oct 2009
Location: Aberystwyth, Ceredigion, UK.
Posts: 103
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Re: Bush TR82
Hi Andy
Are you sure that the audio section works WELL? OK it buzzes, but try connecting a proper audio source across the vol. control just to be sure. If the detector diode has gone you don't need to open the can; just solder the replacement externally across pins 5 and 6 of IFT3. Here's my write up of my OC blessed version:- https://www.vintage-radio.net/forum/...ad.php?t=47112 |
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9th Nov 2012, 6:28 pm
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#5 |
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Hexode
Join Date: Feb 2011
Location: Gloucestershire, UK.
Posts: 376
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Re: Bush TR82
OA 91 between 2 and 3 and 774 Classic Gold romping in. Great audio quality too.
Thanks chaps 
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