I have an older 220 ten tec L network transmatch I am rebuilding, and I
notice that ten tec uses high voltage disk ceramic paddling caps in series
with the main tuning air paddler...
I notice that under some tuning conditions, the swr will drift and some of
the ceramic caps will get rather warm, even with barefoot power applied...
I am wondering if substuting the original ceramic caps with 2nF type caps
will stablized the swr drift.
----- Original Message -----
From: "Jason Cooper" <jbear45@msn.com>
To: <n5oe@nctwb.net>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Saturday, July 21, 2007 3:18 PM
Subject: Re: [TenTec] Titan 425 troubles, R1 and blown 20a fuses
If one capacitor went south, there is a very good possibility that some
others were also very close to failure. You are doing the right thing by
ordering some new ones. There is a possibility of a transformer failure,
however, a Peter Dahl replacement is very expensive and you would have to
replace the caps if you cannot test them at high voltage. I restored a
425 about 6 months ago and tested each capacitor with a variable HV power
supply and an ammeter. After re-forming them, all my caps were well under
200uA at 500V so I did not replace them. If you can get to a HV supply or
a HV curve tracer, you could test the caps and that would give you some
reasonable input if the failure was caused by the caps. Also an ESR test
is useful if you can find someone with an ESR meter. If I remember
correctly, R1 (It's R2 on my schematic) is in the soft-start circuit and
would certainly blow if one of the caps was drawing excess current.
By the way, I just bought a whole lot of 2nF 10KV ceramic capacitors to
replace the plate blocking caps (C6 and C7) These caps have the X5R
dialectric and will drift very little with heat unlike the OEM caps that
Ten-Tec used. This will fix the tuning drift problem on 80M and 160M. I
would be willing to sell off the excess if there is any interest
Good luck fixing your 425. Jason KN7AZ
----- Original Message -----
From: Carlin Royal<mailto:n5oe@nctwb.net>
To: tentec@contesting.com<mailto:tentec@contesting.com>
Sent: Friday, July 20, 2007 2:45 PM
Subject: [TenTec] Titan 425 troubles, R1 and blown 20a fuses
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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