78 are same tubes with different base, correct? Will OPT handle the gain if 7247 is replaced with 12AX7? Of course circuit will have to be modified for that but it could be borrowed from Dave G's modified Fisher 400. I'm not impressed with the gain but it might still be very weak 7247 PI tube. Lucky because I'd condemned circuit fault otherwise. But main amp is GOOD! I wired one of the RCA jacks directly to amp input(10k resistor on pin 5 of 7247 tube) I went through all 7247 tubes I had to only find one that works! So I pulled rectifier tube for that channel and eventually all tubes from that channel.
One of the resistors on 4 section can burned up.
I turned it of and flipped amp to inspect. 6gw8 channel started to crackle at about 80v. I seem to recall that one forum member had solved some difficulties by checking the connectors on his Elegante.Powered up with variac with all 3 original speakers connected. (always spoken with a very loud "touch wood!!). When the power is switched there is a speaker thump….if absent there might be a issue in the amp or the connectors to it.Ĭonnectors certainly are a possibility although have had not much trouble with them on my organ. I was thinking you may want to check the connectors on the amplifier board while waiting for this manual. Organ Service Company has service manuals listed on this page. Do I just clean as many circuit board and wire connectors that I can find and reach and spray them all? Is just spraying good enough if I don't see any corrosion? Also, any idea where to find a service manual for the model 340100? After reading more on the "LSI Disease", it appears to be a major problem with some Hammonds. I don't like it and think it should be more like 70's connector disease. Since this practice was introduced with the LSI era organs, the term LSI disease came about. As long as the connectors are kept clean either by routine cleaning or the equipment being kept in a dry moderate climate the products can be reliable. The problems with 70's organs, (most brands) was the use of plugs and jacks that were built with cheap material. Unless damaged by surges or lightning, they are as hardy as generic IC's found in most all electronics. The vast majority of LSI's from this era are still working. Service Manuals should be available from Jerry Welch at Organ Service Company. The power supply board on the bottom has the voltages written on each connector. The next thing to do is verify all voltages are present. You must verify that the organ is solid mechanically before entering into an electronic troubleshoot. Still, any older organ should have the internal connections cleaned. The "LSI Disease" (a term I don't like) is for earlier models like the Concorde.
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