Hello,
I built a Crack amp with Speedball at the same time, omitting the steps that need to be undone to install the Speedball upgrade: installing the plate load resistors and the output cathode resistors. (yep I ignored the warnings and am reaping what I sowed).
I also followed the revision on page 19 of the Crack manual:
"REVISION 5/6/10:
Making this wire 3†long and
connecting it to Terminal 14U
instead of terminal 22L may
yield more quiet operation."
When I measure the resistances, for the terminals marked '*' I am getting readings in the Mega-Ohm range. Terminals marked '0' I'm reading about 0.2 Ohm, with none more than 0.3 Ohm.
Terminals 6 and 10 read a little high at 2.49 KOhm.
However, terminal 7, terminal 9, terminal 13, B3 and B6 all read at infinity Ohms. The center RCA jacks read 109 KOhm.
When I turn it on, the tube heaters light up, and all the diodes light up.
I measured the voltages at (terminal numbers below):
- 73.3 V
- 179 V
- 1 mV
- 179 V
- 72.7 V
- 0.9-11 mV (varied slightly between these values
- 105.6 V
- 2 mv
- 102.6 V
- 3-11 mV (varied a little, tending to stay about 5mv)
- 1 mV
- 0.1 mV
- 179 V
- 0.5 mV
- 198.6 V
20. 0.5 mV
21. 212.5 V
A1. 73.1 V
A2. 0.6mV
A4. -0.3 mV
A5. -1.2 - 1 mV (varied a little between these observed peaks)
A6. 73 V
A7. 0.5 mV
A9. 0.5 mV
B1. 73.3 V
B2. 178.6 V
B3. 105.6 V
B4. 72.8 V
B5. 179 V
B6. 102.7 V
B7. 0.5 - 1 mV
B8. 0.1 mV
After powering down for 5 minutes, when I power it up, the ring contact on the 1/4" TRS jack spikes close to 21 V before dropping down to the millivolt range where it bounces around between low single-digit millivolts and about 30 millivolts.
I don't suppose these readings are to be expected? (I'm afraid to plug in any headphones with that headphone jack reading that high until I'm certain this is fine.)
Are there some more tests I can do/measurements I can take in this state to narrow down the culprit for the low voltages on the tubes and incorrect resistances?
Thanks for helping an overambitious fool
