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M Board problem - heat related.

pyjamagroove All Messages By This Member #4867 Edited Hi guys, So one of my M Boards (°4 on CH I) goes silent after a warm up. I have established that the tuning goes down to the point that it's not auditable. The problems that it is almost Impossible to trace because when I take it out for inspection it cools down and sounds ok again (in tune! ). Here is what I did so far: 1. Cleaned VCO's legs and applied fresh heat conducting agent between the IC and the diode. 2. I have bought that I have the same issue as MFox (described here ?so I have changed the IC3. Did not work... As I sad the problem is diagnostics. Did anyone have a similar problem?
Florian Anwander All Messages By This Member #4868 开云体育 Hi Am 08.07.22 um 10:19 schrieb pyjamagroove via groups.io: The problems that it is almost Impossible to trace because when I take it out for inspection it cools down and sounds ok again (in tune! )._._,_._,_ I had once a similar issue (a thermal problem disappears when the card is take out and or the lid is open), so I soldered long wires? (about 60cm / 2ft long) to all points on the card I wanted to measure. The wires led to a gridstyle breadboard which could be placed on the keyboard, while the card is mounted and the lid is closed. So I could measure at least a few selected signals of this card on this breadboard while lid is closed. regards Florian
pyjamagroove All Messages By This Member #4869 Thanks Florian for your response. I have to admit that you method is pretty hardcore! Personally I am afraid to do that - I might fry something in the process and there is way to many "points of interest" to check...maybe I will put the card it a sock or something.. What bothers me is that I can't find any topic on the subject (radically heat affected tuning). I suspect the transposition circuit (a FET or transistor going bad).
Gregory Cox All Messages By This Member #4870 开云体育 What I would try is using a hot air station with adjustable temperature and see if I could locate the faulty component that way. ? Greg toggle quoted message Show quoted text On Jul 8, 2022, at 4:25 AM, pyjamagroove via groups.io <pyjamagroove@...> wrote: ? [Edited Message Follows] Hi guys, So one of my M Boards (°4 on CH I) goes silent after a warm up. I have established that the tuning goes down to the point that it's not auditable. The problems that it is almost Impossible to trace because when I take it out for inspection it cools down and sounds ok again (in tune! ). Here is what I did so far: 1. Cleaned VCO's legs and applied fresh heat conducting agent between the IC and the diode. 2. I have bought that I have the same issue as MFox (described here ?so I have changed the IC3. Did not work... As I sad the problem is diagnostics. Did anyone have a similar problem?
Tommy's Keys All Messages By This Member #4871 Hi. Yes, the problem? The IC VCO Socket !! many years ago, with the same problem I resolve only changing the Socket. ? toggle quoted message Show quoted text Il ven 8 lug 2022, 10:19 pyjamagroove via <pyjamagroove=yahoo.com@groups.io> ha scritto: Hi guys, So one of my M Boards (°4 on CH I) goes silent after a warm up. I have established that the tuning goes down to the point that it's not auditable. The problems that it is almost Impossible to trace because when I take it out for inspection it cools down and sounds ok again (in tune! ). Here is what I did so far: 1. Cleaned VCO's legs and applied fresh heat conducting agent between the IC and the diode. 2. I have bought that I have the same issue as MFox (described here ?so I have changed the IC3. Dod not work. As I sad the problem is diagnostics. Did anyone have a similar problem?
pyjamagroove All Messages By This Member #4872 BINGO!? Changed the VCOs socket and all is fine. Thanks Tommy, thanks everyone for your quick responses. Happy end.

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