Hi
I have a HD-130 that i am trying to fix.
I have made some progress with the amp.
The amp has the SS phase inverter board.
After replacing 2 power tubes, I also found a faulty JE 1692 which i replaced with a MJE15030.
it has 4 good tested tubes and powers up
I cannot get any readings other than .1 volt on my bias probes.
I have adjusted the pot on the phase inverter board with no change.
my tubes are glowing.
There are 2 pots on the preamp board. Is the one towards middle for the tremolo?The one on the right side is near the *16v and -16v wires.
and there is a pot on the phase inverter board
Which pot is the one for adjusting tube bias? i am thinking the one on the phase inverter board is the bias pot?
Thanks I am familiar with tube circuits, when i saw the pot on the solid state phase inverter. it looks like the bias pot then im wondering if its a balance pot.
if the 1458 chip was bad. that would not affect the bias correct? i have checked many caps, diodes and resistors but i am unsure which pot adjusts bias. i thought that i would take a break and ask? and also what is that glass bulb for hooked to the mains fuse? is that a slow start? because when i first take out of standby my high voltage seems to take a few seconds to read.
every once in awhile i get varying high voltage but i am using a dim bulb and variac. Something is not right with the high voltage.my bias meter read over 1000 volts last time i powered it up. i adusted the variac back down
thanks for any info!
jack
Fri, 09/22/2023 - 21:01
#1
update: my meter is faulty. i
update: my meter is faulty. i put a good working meter on plate voltage and my plate voltage is reading low at pin 3 on output tube sockets. 250 vdc
meter is okay i have 660vdc
meter is okay i have 660vdc from pin3 to ground. i only have 250vdc going from pin3 to pin8. pin 8 goes to the JE1692. i still dont have any bias reading and 250 vdc on the output tube plate, is that normal for a solid state driven output tube? 250 from pin3 to pin8? sorry for my lack of knowledge on these amps. there is not much info on this model as i would have thought. thanks!
thanks
thanks
Start from Scratch
When an amp is in an uncertain condition, it's always a good idea to verify that all powers supplies are working properly before trying to fix other problems. After removing the tubes, power it up and verify all hi and low voltages are good. Check the low voltages (+/-16V) at the output of the regulator zener diodes (D5,D6,D17) and replace any that have gone bad. It's also a good idea to check the physical condition of all power supply electrolytic caps. Replace any that show signs of leaking or bulging. -mgriffin