Are those resistors carbon-composite types from the 1960's? In that case I wouldn't be so sure that you can eliminate them. We had couple of those in a student lab I was teaching. Every once in a while we found 5.6kohm devices with roughly 200ohms and/or vice versa.
These were unused resistors which were still in their original package, not exposed to anything which might be considered harmful for a resistor during the 30+ years of their shelf life... Uwe. > Recently, Somebody Somewhere wrote these words >> > These are venerable transistors in a TO5 can. The board is a Siemens >> > part, which they have made 'obsolete' without replacing it. This is >> > hardly surprising, as the devices are batch dated '6940' >> > >> > The board is basically a set of interconnected discrete bipolar >> > logic gates, with some intermittent fault. I can find huge gain >> > mismatches, and I want to replace the low gain devices. >> >> I have to ask why you want to do that. Classically, those circuits >> were designed so that the low gain devices work just fine. Excessive >> gain can cause it's own problems. ?? > I have this obsolete board from the Electricity Supply Board's Turlogh > (pronounced Turlock) Hill plant which has an intermittent fault. It has > diodes, resistors, and SST117s. I can eliminate the diodes, the > resistors, and so am left looking at the transistors. > When these boards classically went intermittent, what was the issue? No > capacitors here, beyond a few pF. There's 100pF across one resistor. > The caps don't leak. I can check and exercise them with Analogue > Signature Analysis. >> >> Also, it appears that the SST11x series of JFETs is a clone of the >> J11x series from a different time than the SST117. I think it's >> unlikely that a logic board would have been made from JFETs in 1969. > That's another 'red herring' correctly categorised, then :-) > -- > With best Regards, > Declan Moriarty. -- Author: Uwe Zimmermann INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
