Quote:
Originally Posted by zeno
Most common ways are
1) Zenith. an osc starts the HV via an extra pin on hoz drive.
2) RCA a small voltage from main PS kicks starts the horz, when
the secondaries come up it runs off that.
3) Others PS always running. Hoz osc is turned on / off for on/off.
If you havnt try this.
Unplug DGS coil. Run variac @90 VAC. Monitor current.Must stay under 1 amp.
Start for 1 sec. If high current usually FBT bad & its getting over current
HVSD. If it stays @ .5 A to 1 A run a bit longer & be sure the HOT is staying cool.
A normal SS color 19" + will draw apx 3/4 amp.
Zeno  |
Thanks - FBT new, customer found NOS replacement, installed to make diagnosis easier.
Will check current draw as suggested. Original problem was shorted output transistor, open fuse. Damper diode ok, nothing getting hot after new output installed. B+ around 100, spec 112; may be adjustment problem. No 25VDC line produced, since FBT not running. Provide 25VDC from bench supply, turn set on, 25 volt line draws around 450ma, clean waveform at base of output transistor, no change in the B+. Assumptions from that: IC and horizontal driver circuit OK.
All regulator and shut down components checked with ohm meter and also by lifting one end, no change. Yoke is not in the circuit, but the B+ jumper is installed so good B+ at output transistor collector.
No HV at all, anode lead dead. Again, new FBT so that rules out, I think, bad tripler diodes in the FBT case.
I need to fire up my B&K 1077B and ring the original flyback and the new one; not sure why that was not done first . . . I would just prefer to work with the original part, part number on the new one not exactly the same, customer found it by doing a search for model number part list. This is model CLB216P003; customer found FBT for CLB216P002 . . . .
NOTE: I found a few parts, I forget which at the moment, on the chassis that are not on the Sams, and there is IIRC a suffix letter on the model not shown on the Sams ....
This is model CLB216P003; customer found FBT for CLB216P002 . . . .
More later, I will be back into the set this weekend. I have chassis only.
Need to check diodes and load resistances on secondary supplies, come to think of it, might not hurt check to see if any of the secondaries are even working with the external 25 volts supplied.
Thanks for dealing with my ramble; helps me to focus my thoughts.
Art