G
Gary Vee
New member
I have a Mig Lead 100 Watt 1993 Sovtek amp head and I have a Marshall (1960 A ) cab w/4 - 75 watt Celeston speakers and El 34 tubes , I just changed the tubes to a Quad of Xf2 and Xf3 NOS Mullards 1960-1965 and I just want to make sure it is right ! , It plays good there's no hot glowing plates or anything like that going on but the voltages and currents all seem very unusual to me and I cannot seem to find any really good info on a early Mig 100 Lead Head and this one is using EL 34's , The amp came with 5881 Sovtek tubes when I got it the pristine and was almost new back in 1994 or 1995 and it has been a great amp for my guitar and for my bass also, The amp has had two sets of EL 34's in it now , the pin 1 to 8 jumper wire is gone now so no-more 6L6's and the tube sockets were just replaced by mistake over a bad tube - they were good and the tube was bad . The amp was just fixed by a tech and I tried it with some cheap new EL 34 tubes and it sounded like total garbage with them in it , I Had a Ei Vintage EL 34 Quad in it before until one went bad , so I trashed the cheap sounding new tubes and I decided to go ahead and bite the bullet sell a extra 89 USA Strat that I had so I could get 4 NOS Vintage Mullards , I would like to try to deal with fixing it myself this time plus my tech is old and He has been sick , I have built 10 tube stereo amps and I designed 3 good ones and I taught myself about building tube amps and I was taught Electron Theory a long time ago but this I think is a little bit different then just a basic single stage audio amplifier and some of the stuff inside of it is new to me ! . I just want to get a good tube sound and to save the NOS Mullard tubes from frying themselves up real quick !
There is a pot I see on the output board next to the tone pots that I have not seen before ? plus the readings that I am getting are not really the normal readings that most 100 watt amps have - so I need to get some good advise . I have between 564-578 Volts on pin 3,4 and 6 of the output tubes and it reads ; 10mA , 6mA , 6mA , 10 mA of current flow on the 4 output tubes with a meter between pin 3 wire and the tube , and my negative bias voltage is -57 vdc . I have heard of all of these voltages before in different Mig amps but I just want to make sure that it is ok because everything just seems like it is so far out in space somewhere with all of the high voltage and low mA readings ? ! . The four pin # 8 Cathode resister to chassis is a 1.2 Ohm Brown Black Gold Gold and the four pin # 4 to # 6 power resisters are all 5 watt 1 k . Pin # 1 to 5 resisters are all 4 ; read 1,485 colors are ; Brown Green Red Gold . 3 Black Plates are in the pre amp section , 5171 Sylvania 3 mica Black Plate in # 1 and a RCA Long Black Plates in # 2 and # 3 . I have an Vintage Ei long grey smooth plate coming for # 2 and I was gonna move one of the RCA tubes into # 1 when it gets here. Just need a little help from someone with more experience on guitar amps ? ! here's a few pics of it inside . Thanks Gary !
There is a pot I see on the output board next to the tone pots that I have not seen before ? plus the readings that I am getting are not really the normal readings that most 100 watt amps have - so I need to get some good advise . I have between 564-578 Volts on pin 3,4 and 6 of the output tubes and it reads ; 10mA , 6mA , 6mA , 10 mA of current flow on the 4 output tubes with a meter between pin 3 wire and the tube , and my negative bias voltage is -57 vdc . I have heard of all of these voltages before in different Mig amps but I just want to make sure that it is ok because everything just seems like it is so far out in space somewhere with all of the high voltage and low mA readings ? ! . The four pin # 8 Cathode resister to chassis is a 1.2 Ohm Brown Black Gold Gold and the four pin # 4 to # 6 power resisters are all 5 watt 1 k . Pin # 1 to 5 resisters are all 4 ; read 1,485 colors are ; Brown Green Red Gold . 3 Black Plates are in the pre amp section , 5171 Sylvania 3 mica Black Plate in # 1 and a RCA Long Black Plates in # 2 and # 3 . I have an Vintage Ei long grey smooth plate coming for # 2 and I was gonna move one of the RCA tubes into # 1 when it gets here. Just need a little help from someone with more experience on guitar amps ? ! here's a few pics of it inside . Thanks Gary !
