Hey all. I completed a TSE-II build with 45s a few weeks back, all went great, checked out perfectly and sounded beautiful on my test bench.
I rehoused it this weekend into its newly built case and there's a problem, the output tubes are not heating… here are my voltages:
No tubes installed:
-0.35 VDC B+
-137 VDC B-
5.4 VAC Rectifier Filament VAC (Pins 2-8)
8.26 VDC 5842 Filament (Pins 3-9)
0.48 VDC 45 Filament (Pins 1-4)
5AR4 Rectifier installed:
345 VDC B+
-137 VDC B-
0.46 VDC 45 Filament
5842s installed:
Biased to 175VDC
331 VDC B+
-137 VDC B-
5.85 VDC 5842 Filament
0.44 VDC 45 Filament
I think all checks out good except the 45 heater voltages; obviously expecting 2.5 VDC here. Resistors all check out fine. Any help greatly appreciated!
I rehoused it this weekend into its newly built case and there's a problem, the output tubes are not heating… here are my voltages:
No tubes installed:
-0.35 VDC B+
-137 VDC B-
5.4 VAC Rectifier Filament VAC (Pins 2-8)
8.26 VDC 5842 Filament (Pins 3-9)
0.48 VDC 45 Filament (Pins 1-4)
5AR4 Rectifier installed:
345 VDC B+
-137 VDC B-
0.46 VDC 45 Filament
5842s installed:
Biased to 175VDC
331 VDC B+
-137 VDC B-
5.85 VDC 5842 Filament
0.44 VDC 45 Filament
I think all checks out good except the 45 heater voltages; obviously expecting 2.5 VDC here. Resistors all check out fine. Any help greatly appreciated!
Some more info, I traced voltages from the 6.3V heater input through D1 and IC3:
D1 Input (pins 1 & 3): 3.29 VAC
D1 Output(pin 2): 3.67 VDC
IC3 Input (pin 2): 3.67 VDC
IC3 Output (pin 4): 0.4 - 0.7 VDC fluctuating!
My limited knowledge of ICs says these numbers don't look good - would be great if anyone could chime in before I start trying to desolder!
D1 Input (pins 1 & 3): 3.29 VAC
D1 Output(pin 2): 3.67 VDC
IC3 Input (pin 2): 3.67 VDC
IC3 Output (pin 4): 0.4 - 0.7 VDC fluctuating!
My limited knowledge of ICs says these numbers don't look good - would be great if anyone could chime in before I start trying to desolder!
Measure the DC resistance between the two filament pins with no power and no tubes installed, just to see if something got shorted. Then power it up and measure the adjust pin on the regulator. it should be about 1.25 volts. If not make sure that R1 and R2 are not physically damaged.
Thanks for the quick response. I'm getting ~0.6 Ohm across the filament pins on each socket and only 0.19 VDC on the adjust pin 5 on the regulator IC3.
R1 and R2 look fine, measure 50 Ohms each in circuit...
R1 and R2 look fine, measure 50 Ohms each in circuit...
The input voltage to the regulator must be low too. That could be caused by excessive
output current, dropping out the regulator. If the input voltage is too low even without
tubes plugged in, find out where the excess current is going.
output current, dropping out the regulator. If the input voltage is too low even without
tubes plugged in, find out where the excess current is going.
0.6 ohms between the filament pins is too low with no tubes installed. Carefully check for solder bridges at the socket pins, and check the polarity of all the electrolytic caps.
Did you make any changes in the board especially around the regulator or output tubes when transplanting it into a chassis? If so check that area carefully for a short.
Did you make any changes in the board especially around the regulator or output tubes when transplanting it into a chassis? If so check that area carefully for a short.
Okay fixed. I'd mounted my board inverted under an aluminium top plate with brass standoffs. Now I knew the standoffs were close to the 45 sockets but hadn't realised they were actually touching the metal surrounds... well both were shorting.
Thanks for the responses - helped me down the right track!
Thanks for the responses - helped me down the right track!
Attachments
Ihad a similar issue with a mounting washer cutting through a trace. Removed washer and problem solved. I'd say if you use washers, make them nylon.