[TMC] PRogress report No. 3?

[telegrapher at att.net]

Things are looking up.  We we last parted i was fretting about the PA 
overload circuit breaker popping when i turned on the HV through the 
Transmit voltages switch.  That's the sequence, turn on the HV switch 
and then when the transmitter is keyed either with the switch on front 
of the PS-4 or through a mic PTT or other ways.

I'd previously discovered that the 90K bleeder was cracked and wide open 
so while i had found one locally, i couldn't get it till this coming 
weekend, i had ordered a pair of 50K @ 100W units from a supplier.  they 
arrived on Monday.  Great service from these folks.  So Monday PM i 
spent building up a replacement assembly to hold the nw bleeder repairs. 
  After getting that all constructed, mounted into the same place as the 
old resistor went and wiring it up and checking continuity along with 
other places for shorts and grounds i put the cover back on the top of 
the HV supply.  Hooked AC to the cabinet again and proceeded with the 
power up sequence.  Everything goes fine till turning on the 
"Transmitter" voltages switch.  Momentary pause then the Ip overload CB 
pops and then the Main power on the PS-4 low voltage supply kicks off.

I knew i had the problem fixed. I just knew it.  Ha!  Back to the books. 
  Well in the trouble shooting section for the PAL-1K it says under the 
troubleshooting of the HV supply section, to replace one or both of the 
872 rectifiers.  I'd thought about this because when i turned on the 
Transmitter voltages switch i saw a flash at the bottom of one of the 
872's.

Out to the storage shed to retrieve a new pair of these beast's.  Pull 
both the old ones out and put the new ones in.  Start the power up 
sequence again.  After a few minutes it was time to turn on the HV 
switch.  The timer in the PS-4 had kicked in so things were going well. 
  HV switch on, now for the Transmitter voltages.  Where's a long stick? 
  Turn the Transmitter voltages switch on and there it was!  A red and 
green light showing all the voltages were up and going.  3Kv on the 
meter for Ep.  100V bias and about 450 V for screen.  Things are good!

I don't know if there is any break in period or particular processes 
for getting the 872's up and on line properly or not but i've had the 
transmitter on with all voltages, no drive, applied for several hours 
now and it's really running nicely.

One thing i'm not sure about is the fact that when i adjust the mid 
voltage to 500v (per the manual) the resting plate current also 
increases.  This voltage is for the 6146 driver and not the PL-172 PA 
tube.  Resting Ip should be 220 ma.  Evidently i've got more to learn 
about this beast.

Maybe tomorrow i'll take the HP sig gen out and use it for drive to the 
PA and see how things are while continuing through the tune-up process.

At least most of the problems have been overcome.  Now i can hope that 
the final is ok and not flat.  No way this thing has worked since who 
knows when.  To many problems were in it from wiring to tubes.

Now to get the replacement choke in the VOX and hopefully that will 
bring that unit on line and i can get it mounted back in the cabinet.

Assembly and checkout of one of these things is not by the book.  After 
you've put it together, then you find out that you should have done this 
or that before putting the screws in the panels or added this wiring 
before you put that panel in place because if you didn't, then you've 
got to pull this panel out and loosen this one up before you can get the 
panel out that you need to work on.  Course if this stuff was installed 
"turnkey" then the installers would have a wire running list and it 
would go a lot smoother.  With the unskilled types like some of us 
owners are, we live and learn the hard way.

I'm smiling again!!!!!

Larry
W0OGH




I disconnected the HV line to the PA and the CB opened up again when i 
went through the HV turn on sequence.  Disconnect the AC, pull HV supply 
out of rack, open it up, discharge the caps (think safety) and look around.