I would keep an eye on the resistor, for heating. Also did you check the voltages for correct levels?Hi Chuck,
At some point I will probably upgrade my Quadram with the information you sent. I went back at the Quadram power supply and I could see the first band on the burnt resistor and it was orange. I measured the bad resistor and it measured 359 ohms so I thought maybe it only marginally changed value. Knowing that the first band was likely orange I decided that the original value was most likely 330 or 390 ohms so I dug out a 390 ohm resistor, soldered it in and it worked. The additional memory, clock, floppy and parallel port now work however Drive A was still and issue. I always had a problem with drive A whenever the Quadram was installed but it worked fine when the Quadram was removed. I had tried different cables and cleaning connections but that didn’t work so I was hoping that changing the capacitors on the power supply would fix this issue as well but it did not. But reading through the memory modifications for the Quadram you sent the last paragraph mentions issues with shielding. So I fabricated some shielding for the Quadram extension board and I was very happy that this cleared up the Drive A issue. I now have a fully functioning Quadram system.
Thanks again for the documentation.
Nice to get one of these old specialty units back up and running, upload a couple pictures would love to see them..