| Author | Message | ||
| meaty |
Well i gotta admit this site has given me a new hobby - excellent work Steve thanks you. Description: MM 112/RD , 1 input channel hi & low sockets.. footswitch with distortion & reverb both work well & have seperate gain & volume controls on the amp itself. Badges are black background & the men are silver Chassis # 2165rd , Serial # DNO3668 ID #2100 Now steve a little knowledge can be dangerous , so ill let a tech do the high voltage and caps check etc The amps has 2 tubes stamped STR 387,SYLVANIA 6L6GC, USA These tubes need to be re-biased, when this is done will these tubes supply me with a warm bluesy feel or should i u use a different tube to acheive this secondly from the description i have given u of the amp do i download the gd-1 diagram ? or do i pull the head out of the amp out to check it , if so how do i remove it and what pitfalls should i watchout for . I imagine that many more question will follow . thanks again Steve | ||
| Steve Kennedy |
The GD-1 schematic is for the oldest RD amplifiers... the ones that most certainly would have silver badges with the little men in black. In the GD-1 circuit, a relay switched in or out the two different sets of gain & volume controls in order to simulate channel switching. Also, the output tubes were 6CA7/EL34 types. The GD-2 circuit uses electronic switching that actual modifies the signal path beyond simply substituting control pots. It is a much more sophisticated and reliable arrangement. This version uses 6L6 output tubes like yours. The Sylvania STR387 6L6 tube is a highly regarded tube and should sound noticeably better than the Sovtek/EH "5881" type tubes currently being sold as 6L6 replacements. Sound quality is a personal thing so your mileage may vary. If you remove the chassis from the cabinet, make sure you first remove any screws affixing cable restraint loops that may be tying the power cord to the cabinet. Also, remove the footswitch connections and output tubes. Gently remove the chassis from the rear by wiggling and holding onto the power transformer. If you don't suypport the transformer while removing the chassis, the center of gravity WILL shift once it is clear of the cabinet and the chassis could be dropped face down or it could swing down smashing into a body part or can actually cut your fingers if you aren't careful. As always never remove a chassis that has recently been turned on.... let it rest for a long while to help discharge the internal filter caps first. High Voltage of this caliber can KILL you! Steve | ||
| meaty |
http://65.173.181.17/cgi-bin/discus/show .cgi? HI Steve , well i got the head of the amp out , the board is dated 17th Jan 1986 and i found the origional diagram its a GD-2A , so im off to the amp tech sometime this week , i have 1 leaky cap and ill get the tubes biased as well the 6L6 tube is shown on the diagram ill try to get a pic of the amp scanned if u want steve thanks again for your help !!!!!  | ||
| Steve Kennedy |
17 Jan 1986? From everything I have seen Music Man was out of business and liquidated by the first half of 1985. I wonder if your amp was made from amps and parts sold after the company stopped doing business? If the date is handwritten, I might be 198something else. Steve | ||
| meaty |
hummmmm - maybe i didnt have my glasses on steve ill remove the head again and double check it enjoy!!!!!!! | ||
| meaty |
the date is hand written -hows the 17th of jan 1980 sound steve- lol it took a GOOD magnifing glass to see it still looks like 1986 with the naked eye tho all is in order GD-2 diagram , black badges with silver men 1980 on the board. pics will follow in about a week see ya soon - ENJOY!!!!! | ||
| Steve kennedy |
That sounds better...and everything matches up! I look forward to the pictures! Make them as close-up and detailed as you can... too many people show their entire room and the amp is only 1/4 of the frame! Steve |
Tue, 03/25/2014 - 09:28
#1