need a volunteer to test a pre-driver board design
Hi, Yamaha fans,
Hope this thread isn't too ancient to pick up again. I thought it was the right place for this.
I've done a PCB design for a drop-in IG02930 replacement, based largely on merrylander's research. I did the design for my own use in restoring a couple of CR-1040s, and for fun. I'd like to both make the board layout available for free, and eventually sell a few finished boards to help offset the entertainment cost. But first, I'd like to find a volunteeer to be a "beta tester" - to take one of the finished boards and test it independently.
If you volunteer, what I propose is to send you a finished module for your use in repairing a CR-1040 (or CR-840 - the same board should work fine there). There would be no cost to you, and the board would be yours to keep. The only obligation is that you let me know how it works for you.
There are a few requirements: you need an address where the USPS can deliver; a CR-1040 (CR-1040) with a known bad IG02930 (IG02940); and enough experience with this sort of repair that you'll have no trouble DIYing it. In particular, you'll need to be able to remove the bad part, install the new board, verify whether the receiver is working properly after replacement, and do the DC offset adjustment that's a normal part of this repair.
If you can be the volunteer, send me email with your USPS address. I'm only offering one board, so if there are several volunteers, I reserve the right to pick one. If you like, include a brief note in the email telling me a little about your repair - I'll use that to pick a volunteer if necessary. It would be particularly relevant to discuss how you'll make sure there are no problems elsewhere, like with the power output module and its associated emitter resistors.
Let me say a little about the board design. I'll try to include a picture, which will show that the board is about the same width as an IG02930, but quite a bit taller - there's plenty of room in that direction.
The amplification section of the board is faithful to merrylander's
schematic, and I've verified that it duplicates the original IG02930's
open-loop gain and bandwidth. (The board you will receive has been tested for those parameters, as well as DC offset.)
The other section of the board has the function of limiting current in the power amplifier's output stage. I'm suspicious of this part of the design, given that output module and emitter resistor failures are releatively frequent in Yamahas. I've modified it a bit, mostly copying from Marantz SR-6000DC. That Marantz model had a very similar power amplifier design to the Yamahas, but as far as I can tell isn't so prone to output problems. The modified circuit limits the current at the same level as the original, but is notably faster-acting. Its speed is set by on-board capacitors, rather than the ones on the Yamaha main circuit board.
Components were chosen from contemporary sources with good availability. Semiconductors are from the Fairchild line. Attention has been paid to thermal coupling for matched transistor pairs, and thermal dissipation for parts that generate appreciable heat.
(Edit: removed my direct email address. Only about a decade later. Guess it was never a problem to begin with, but times being what they are, I figure I'd better tighten things up. Anyone looking for Merrylander's schematic can find it in the media section of my profile pages here.)
