Hi Carlin,
If one electrolytic capacitor in the bank is known to be bad, the rest
of them should be expected to go bad soon. Faults in the capacitor bank
could stress the diodes in the rectifier. You probably will save time,
trouble and money by replacing all of the capacitors and all of the
diodes, before powering it up again. My schematics for my 425 are
apparently not similar enough for me to find the resistor you have
smoked, so it is difficult to guess the cause of it's demise. (My AC
BOARD SCHEMATIC has two different R2s and an R1 which is 20 ohm 25 watt,
but you said the R1 you have trouble with is on a different board)
Failures or arc overs inside the RF deck can also blow fuses and other
components in the power supply. I suggest a thorough inspection of the
RF deck and the interconnecting HV cable before energizing it again. Get
the dust out of both the RF deck and the Power Supply.
I find it difficult to believe that a failed transformer would burn out
parts in the secondary, HV rectifier and filter capacitor, parts of the
circuit, although it certainly could blow fuses and other parts in the
transformer primary circuitry. For the sake of your pocketbook,
hopefully the transformer is still good.
Do not bypass any safety interlocks. Make sure it is not connected to
the AC mains when working on it.
Good luck and work safely.
DE N6KB
Carlin Royal wrote:
I have a Ten Tec Titan 425 that I have only had myself for about 6 months now.
The amp when I received it had 1 bad HV capacitor in the power supply. Due to
lack of funds at the time I replaced the one known bad capacitor. A few months
later I was operating the amplifier during a cw pileup for about 30 minutes, I
set everything on standby and went to lunch. When I returned to the shack I
find the amp had blown one of the 20amp fuses in the supply.
After checking in the PS, I found that R1 the 10ohm 25watt wire wound resistor
on the rectifier board had went open. I replaced the blown resistor and powered
the amp back up, this time again blowing a 20ampfuse and the same resistor. Ten
Tec advised to replace the original rectifer board with a new one, (82112 rev E
I beleive) since they thought some diodes were probably leaking and was the
cause of all my troubles. Now after replacing the old rectifier board with the
new one from Ten TEc, I power the amp on and it blows another 20amp fuse but
did not appear to fry the resistor this time. Here is the main question to the
list; Could I have another bad capacitor that is failing under high voltage
since they do not read any shorts on the VOM when individually beng tested. I
have on order 8 new 400uf 450v caps from Newark Electronics and will be
replacing them this week, but I am looking for more input as to the trouble. It
just seems odd to me that when sitting idle for just 3
0 minutes the thing went south and now I have had all this trouble. Hopefully
I am on the right track and it will be one of the caps in the PS, but would be
interested to hear any other areas that I might could check within reason here
on the very limited bench. Thanks for any advise/comments.
73
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