BYOC 50 Watt Plexi Build Help!
Posted: Sun Jan 08, 2017 3:58 pm
Hi everyone, I just finished wiring up my BYOC 50 watt Plexi Kit. Everything was going great, the light turned on when I powered it up, but when I went to take the test measurements for voltage, I was not getting the expected 490 V on the 1st 32uF capacitor - I was getting like -60mV? I put all the tubes in and they are all glowing OK (tubes are new and from my Marshall JCM900, so I know they are OK). However, I am getting NO sound from the amp at all. Speaker cab and speaker cable are OK - tested with my other amp. When I tried to bias the power tubes, the plate voltage is 655V (I am using EH6CA7 tubes). The bias reading on pin 1/8 do not make any sense - I think less than 1 mV.
I downloaded the Metroamp 50 watt instructions and took all the voltage measurements found in there (with power and Standby set to ON). They are way off:
Tube:Pin1; Pin2; Pin3:Pin4:Pin5:Pin6:Pin7:Pin8:Pin9
V1: 124mV; 0; 0; 3.56VAC; 3.56VAC; -133mV; 0; 0; -1.3mV
V2: 124mV; 0; 0; 3.56VAC; 3.56VAC; -133mV; 0; 0; -1.3mV
V3: 124mV; 0; 0; 3.56VAC; 3.56VAC; -133mV; 0; 0; -1.3mV
V4: 0; 3.57VAC; -131mV; -132mV; 13.6-22.4mV (bias pot min and mx); -136mV; 3.56VAC; 0
V5: 0; 3.57VAC; -131mV; -132mV; 13.6-22.4mV (bias pot min and mx); -136mV; 3.56VAC; 0
Off side of MAINS switch = 126VAC
3A rear panel fuse = 30.4mV on both sides
500A chassis fuse = 345.9V (circuit board side) and -156.7V on other side
Any help would be very much appreciated! This is my first attempt at an amp build.
I downloaded the Metroamp 50 watt instructions and took all the voltage measurements found in there (with power and Standby set to ON). They are way off:
Tube:Pin1; Pin2; Pin3:Pin4:Pin5:Pin6:Pin7:Pin8:Pin9
V1: 124mV; 0; 0; 3.56VAC; 3.56VAC; -133mV; 0; 0; -1.3mV
V2: 124mV; 0; 0; 3.56VAC; 3.56VAC; -133mV; 0; 0; -1.3mV
V3: 124mV; 0; 0; 3.56VAC; 3.56VAC; -133mV; 0; 0; -1.3mV
V4: 0; 3.57VAC; -131mV; -132mV; 13.6-22.4mV (bias pot min and mx); -136mV; 3.56VAC; 0
V5: 0; 3.57VAC; -131mV; -132mV; 13.6-22.4mV (bias pot min and mx); -136mV; 3.56VAC; 0
Off side of MAINS switch = 126VAC
3A rear panel fuse = 30.4mV on both sides
500A chassis fuse = 345.9V (circuit board side) and -156.7V on other side
Any help would be very much appreciated! This is my first attempt at an amp build.