|Re: Topcat HP-97 with very dim LEDs|
Message #6 Posted by Michael de Estrada on 28 Nov 2009, 11:05 a.m.,
in response to message #5 by Katie Wasserman
My layout matches the layout in the service manual, except that there are only 3 resistors on the top right side, instead of 4 and there is a small cap (?) just below the right side of U4. The S/N is 1909Axxxxx, 4th year of production, so HP may very well have made some changes.
Update: I just got the Museum DVD set V7 and looked at the HP-97 Service Manual. It is now clear that my PCB version has all the resistors except R2, however, the P/N on the cathode driver U1 is the same. Also, the manual troubleshooting guide makes no mention of my condition, namely, all LED segments/digits working correctly but just very dim. So maybe there is something else at work here? I do know that on my other Topcats if I increase the voltage at the battery terminals, the display will get brighter, but on this one it seems to have no effect. Anyway, I'm waiting for a replacement printer idler gear replacement to arrive, so I can run the diagnostic program to see if it reveals anything.
Edited: 28 Nov 2009, 7:44 p.m.