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[TenTec] Titan 425 Major H/L Voltage drop

To: tentec@contesting.com
Subject: [TenTec] Titan 425 Major H/L Voltage drop
From: Carlin Royal <n5oe@nctwb.net>
Reply-to: n5oe@nctwb.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 02 Dec 2010 23:08:30 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Hello group,

I am having an issue with my Titan 425 that has me baffled. Upfront let 
me say I am only a beginner with electronics and have limited equipment 
to work with. The symptoms are obvious voltage drop being shown on the 
panel meter/s of the RF deck itself. Upon a successful startup/warm up 
everything appears normal. High voltage registers around 2.7kv and the 
low voltage (assuming 28v) panel lights are nice and bright. When I 
attempt to key down and tune the amp with basically any amount of input 
power (say 10-20w) the panel lights nearly go dark and my high voltage 
drops well below 2kv and more.

About 3 years ago I reported a somewhat similar problem with blown fuses 
after an earlier problem as well as having a terrible buzz on my signal. 
I bought a new Peter Dahl transformer, all new filter capacitors, and 
ordered the new "upgraded" rectifier board from TenTec. These were all 
installed by a reputable repairman and the amp worked great for several 
months. Then this issue with voltages started sporadicly. Sometimes when 
you turned the amp on and operated it, it would work absolutely fine for 
hours. The next time you turned it on, it might do as described above 
with the voltage drops. Finally after about a month or two of this, the 
am now just has the voltage issues.

After much thought with what little knowledge I have on these things, 
that the K1 power relay my either be weak and/or had dirty terminals. I 
removed it, disassembled and cleaned the contacts as well as verified 
the functionality with a disparate 115v source through the coil. It all 
checked good. I have also verified my supply voltage at the outlet and 
checked for any loose wiring in the shack. I have also re-seated all the 
connections in the power supply leading out of the new transformer. 
While in the power supply however, I noticed that the large 10ohm 25w R2 
resistor on the rectifier board was burned up,,, so I replaced that as 
well. When everything was back together, I tested the amp again with the 
same voltage drop results as before. As a last attempt and to for sure 
verify K1 was not the trouble, I bypassed it all together and switched 
the amp on simply with the 30amp 220v shack breaker, again with no 
change in results.

I am way above my knowledge level here, and was hoping this reflector 
could give me some ideas  and further things to check before having to 
ship this in for repair again. I have the original manual with a 
schematic that I can fumble through, so any advice please reference your 
answers to things I can physically identify and look up in the manual 
and power supply itself.

Thanks in advance

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