[TMC] PRogress report No. 3?

[Mac McCullough]

good report  thanx



Located 46 miles due North of the Alamo, and 121 miles due South of the 
Western White House.   see my website at  www.collinsandharrisradios.com
----- Original Message ----- 
From: <telegrapher at att.net>
To: <TMC at mailman.qth.net>
Sent: Thursday, November 03, 2005 9:45 PM
Subject: [TMC] PRogress report No. 3?


> 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.
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