[TechAssist] TOA " 900 series " (A-912A) mono PA amp no output(in protect)
- From: "Philip Bader" <pbader@xxxxxxxxxxxxxxx>
- To: "Techassist" <techassist@xxxxxxxxxxxxx>
- Date: Sun, 5 Feb 2006 12:57:47 -0500
(Guys, thanks for the help on the Zenith PTV I submitted a few days ago.All
good info.)
Now:
A school I was called out to last week has this Public address amp up in the
press box for the sports field. Has power,front meter lights but the relay
never clecks on(in protect). It's a silver finish anout the size of a large
home amp.
All four power outputs are OK. There are a number of driver transistors on a
seperate board shorted.Some have been replaced a number of years ago,some
are NTE's. I have no diagram or even a parts list.I would like to replace
them with original transistor part numbers.
List of bad transistors I found and the numbers on them:
Q101, NTE90
Q103, NTE123AP
Q104, NTE123AP
Q106, B647
Q108, D667
other small surrounding transistors that "seem" to check OK:
Q103, NTE90
Q105, B647
Q109, D667
Q112, (?)
Even a parts list would help.There are a few dark resistors as well.
This looks pretty heavy duty with a huge audio output transformer.
Even tho the previous tech used NTE's they have held up good for about 3
years.
Schemo or parts list please? Any assist welcomed...
Thanks.
Phil
Philip Bader
Polk County School Board
Electronics Shop, Bartow,Fl.
(former owner, Jan Phyl TV Inc.,Winter Haven, Fl. from 1976-2006)
email: pbader@xxxxxxxxxxxxxxx
phone # given by request
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