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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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HH IC100L amp from 1977
Been used as 1ch amp for 20 years but now wanting ch2 up and working.
Someone in the 80s must have tried repairing, replacing a TBA231 with a 741 where it was a blown associated 741 , still there,now changed, that was probably the problem. TBA231 unobtanium (sensibly) datasheet http://www.bg-electronics.de/datenbl...ise/TBA231.pdf Have tried cobbling together 2 x LM301 wired onto a DIL socket and have the ch2 working but fixed volume. Vol pot is fine. What would be the generic name for this sort of vol control, wiper to gnd and track ends of pot via loads of Rs and Cs to the dual TBA B side output and inv i/p of A and inv i/p of B , be called? The ch1 vol control is the same wiper gnd and that is working order and the wiring looks the same . |
#2
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HH IC100L amp from 1977
The volume is fixed, at probably 50 percent
There are 6.8uF electrolytics in the circuit. Would the circuit configuration be bass-boosted at low volume, to avoid the need for a 4 terminal pot? |
#3
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HH IC100L amp from 1977
N_Cook schrieb:
Been used as 1ch amp for 20 years but now wanting ch2 up and working. Someone in the 80s must have tried repairing, replacing a TBA231 with a 741 where it was a blown associated 741 , still there,now changed, that was probably the problem. TBA231 unobtanium (sensibly) datasheet http://www.bg-electronics.de/datenbl...ise/TBA231.pdf Hi, a few minutes ago I sent you an e-mail and offered one piece for free. Unfortunately, the mail bounced. What a pity ... shrug Bye Reinhard |
#4
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HH IC100L amp from 1977
All electros have good ESR.
The grounded wiper circuit is probably like the vol controls on this HH schematic http://s197.photobucket.com/albums/a...lifier1of2.jpg The IC100 amp involves a pair of 4.7 ohm resistors around the TBA opamp pairs of each ch |
#5
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HH IC100L amp from 1977
Disconnecting the R-C of 100nF+4.7R (lag input A x2 pins of the TBA231
and B the same) from the 2x LM301 p1-p8 f-comp pins, returns something like normal vol/tone function in comparison to ch1. Will have to take some ch1/ch2/f comparison readings |
#6
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HH IC100L amp from 1977
"N_Cook" wrote in message ... Disconnecting the R-C of 100nF+4.7R (lag input A x2 pins of the TBA231 and B the same) from the 2x LM301 p1-p8 f-comp pins, returns something like normal vol/tone function in comparison to ch1. Will have to take some ch1/ch2/f comparison readings Have you not seen the post from Reinhard offering to send you the correct opamp to save all this ****ing about ? Arfa |
#7
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HH IC100L amp from 1977
On 25/08/14 19:51, Reinhard Zwirner wrote:
N_Cook schrieb: Been used as 1ch amp for 20 years but now wanting ch2 up and working. Someone in the 80s must have tried repairing, replacing a TBA231 with a 741 where it was a blown associated 741 , still there,now changed, that was probably the problem. TBA231 unobtanium (sensibly) datasheet http://www.bg-electronics.de/datenbl...ise/TBA231.pdf Hi, a few minutes ago I sent you an e-mail and offered one piece for free. Unfortunately, the mail bounced. What a pity ... shrug Bye Reinhard His current email is on http://www.divdev.fsnet.co.uk/ Not everyone who posts to usenet uses a real email address in headers, including me. I'm actually a multimillionaire that owns a jet boat, an airliner and half a country. Just don't want Nigerian scammers fishing for some of that. -- Adrian C |
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