SEM Noise Eliminator problem - UK Vintage Radio Repair and Restoration Discussion Forum

Lasse_radio · 26th Jul 2010, 5:49 pm

I have got a SEM QRM Noise Eliminator. It has worked perfectly, but yesterday it stopped with no reponse to input from the Gain pot nor the two Phase pots. Signal is supressed slightly when the unit is turned on like it allways has. The large resisistor is going hot and also the relay next to it. I'm not sure what has happened. I had quite alot of static from the longwire, if that could have damage it somehow. But not more than ususal, I believe.

Ha s anyone any information that could help me fix it?

Regards

Lasse

Lasse_radio · 26th Jul 2010, 10:17 pm

In a fine review of the SEM by Bob Eldridge, he mention that he accidentally blew the transistors when testing it. It seems like they are sensitive to wrong input, which could be f ex. static electricity. I'm novice here, so I have not a clue. If this is the case, those transistors could be replaced. The problem is that two of them, (J-Fet n-channel types) have got the numbers erased. If anyone knows what kind of J-fet's could be used as replacement I would be very thanks. It would be a pity to throw it in the waste bin.

A question regarding operation of the SEM ( I do not have the manual). Should the relays be energized, click on, when the unit turns on?

Regards

Lasse

26th Jul 2010, 5:49 pm	#1
Lasse_radio Retired Dormant Member Join Date: Jul 2010 Location: Lund, Sweden Posts: 4	SEM Noise Eliminator problem I have got a SEM QRM Noise Eliminator. It has worked perfectly, but yesterday it stopped with no reponse to input from the Gain pot nor the two Phase pots. Signal is supressed slightly when the unit is turned on like it allways has. The large resisistor is going hot and also the relay next to it. I'm not sure what has happened. I had quite alot of static from the longwire, if that could have damage it somehow. But not more than ususal, I believe. Ha s anyone any information that could help me fix it? Regards Lasse

26th Jul 2010, 10:17 pm	#2
Lasse_radio Retired Dormant Member Join Date: Jul 2010 Location: Lund, Sweden Posts: 4	Re: SEM Noise Eliminator problem In a fine review of the SEM by Bob Eldridge, he mention that he accidentally blew the transistors when testing it. It seems like they are sensitive to wrong input, which could be f ex. static electricity. I'm novice here, so I have not a clue. If this is the case, those transistors could be replaced. The problem is that two of them, (J-Fet n-channel types) have got the numbers erased. If anyone knows what kind of J-fet's could be used as replacement I would be very thanks. It would be a pity to throw it in the waste bin. A question regarding operation of the SEM ( I do not have the manual). Should the relays be energized, click on, when the unit turns on? Regards Lasse