mecha
Well-known member
Polo #1:
symptom: HV present (the tube creates lightning when you discharge it), but no heater glow.
what I've tried so far:
all signs point to checking R35 on the neckboard and anywhere else there for bad solder joints. I went for the gusto and even removed the neck socket and resoldered it back in. there's no signs of any bad joints. resistance check on R35 yields 1.4 ohm, guessing that's within tolerance (it calls for 1 ohm). if you meter each side of R35 to the corresponding pins on the neck socket (5 and 6) continuity checks out between the resistor and the neck pins. HOWEVER, when you check between neck pins 5 and 6, it reads open. I'm guessing this is my problem. does this mean the neck socket is bad?
it's worth noting one of the 250V/100uF caps had a leg that came detached (replaced both 250V/100uF caps in each corner). there was also a trace along the back edge that was severed going to one of the big resistors on the other side of the HOT heatsink. I re-ran wire along the run of that trace.
just in case the replacement flyback I dropped in was no good, I took one of the old known-good flybacks I had and swapped it in. no change.
B+ was tested at 140VDC.
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Polo #2:
symptom: no power at all. not even a click from the HOT.
what I know:
this chassis worked perfectly fine. after the other one lost heater glow I popped this one in my KI2 and it died on the spot... when I ran it on a loose tube about 20 minutes previous and it worked fine.
what I've tried:
fuse is good -- no solder joints look suspect. checked B+ at TP6, I'm getting 0.2VDC. the Fromm flowchart calls for replacement of ZD101 and check C112 in the event of "low B+".. but that was replaced in a cap kit. in the event of "0VDC B+" it calls for checking if R103 is open (it was not) and to test diodes D105-D112 (I tested all of them). the only other thing I haven't tried that it says is replacing IC101. how can I tell if IC101 is bad?
Polo 1 is pretty nasty with holding charges in the neckboard btw, so I don't like powering that one up too much.
to my knowledge, that's the only one of my Polo chassis that does that. does that have anything to do with the heater circuit being flaky?
symptom: HV present (the tube creates lightning when you discharge it), but no heater glow.
what I've tried so far:
all signs point to checking R35 on the neckboard and anywhere else there for bad solder joints. I went for the gusto and even removed the neck socket and resoldered it back in. there's no signs of any bad joints. resistance check on R35 yields 1.4 ohm, guessing that's within tolerance (it calls for 1 ohm). if you meter each side of R35 to the corresponding pins on the neck socket (5 and 6) continuity checks out between the resistor and the neck pins. HOWEVER, when you check between neck pins 5 and 6, it reads open. I'm guessing this is my problem. does this mean the neck socket is bad?
it's worth noting one of the 250V/100uF caps had a leg that came detached (replaced both 250V/100uF caps in each corner). there was also a trace along the back edge that was severed going to one of the big resistors on the other side of the HOT heatsink. I re-ran wire along the run of that trace.
just in case the replacement flyback I dropped in was no good, I took one of the old known-good flybacks I had and swapped it in. no change.
B+ was tested at 140VDC.
---
Polo #2:
symptom: no power at all. not even a click from the HOT.
what I know:
this chassis worked perfectly fine. after the other one lost heater glow I popped this one in my KI2 and it died on the spot... when I ran it on a loose tube about 20 minutes previous and it worked fine.
what I've tried:
fuse is good -- no solder joints look suspect. checked B+ at TP6, I'm getting 0.2VDC. the Fromm flowchart calls for replacement of ZD101 and check C112 in the event of "low B+".. but that was replaced in a cap kit. in the event of "0VDC B+" it calls for checking if R103 is open (it was not) and to test diodes D105-D112 (I tested all of them). the only other thing I haven't tried that it says is replacing IC101. how can I tell if IC101 is bad?
Polo 1 is pretty nasty with holding charges in the neckboard btw, so I don't like powering that one up too much.
