With the amp wired for 230 V, I doubt with only 120 V applied, the low
voltage {as it will be 1/2 of the volts needed for the filaments and the LV
supply} will not be adequate to pull in the relays and thus get the HV
going.
A couple of approaches; one is using two 150 watt 120V light bulbs. Wire
each one of the 150 watt light bulbs in series with each side of the 230
volt line. If there is a major short the bulbs will light to full
brilliance. This basically will limit the inrush current. However the amp
still won't receive full voltage and will not be fully operational. A
second approach is using a Variac. This way you can control the voltage
applied and bring it up slowly and under control. You should measure the
voltage applied as you increase it and also the AC current, watching for any
unusual or rapid changes. For this you'll need a 230 volt Variac rated at
10 amps minimum.
73
Bob, K4TAX
----- Original Message -----
From: "Bry Carling" <bcarling@cfl.rr.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, February 02, 2014 9:31 PM
Subject: Re: [TenTec] TT 422 Blowing Fuses
Thanks guys,
It does appear that I was partly mistaken about how the soft start circuit
works with the three
relays.
Power is indeed applied to the transformer whenever AC Power switch is
turned on and the
interlock is closed and the 12V is applied.
I think this amp has some quite a complex circuits. it is a device that I
had not studied at all
before. Having so many interacting PC boards, I may have misunderstood the
sequence at
turn on for the two main switches. I hope that I have enough smarts left
in me to figure this
out carefully, and understand what is going on when the HV transformer
gets back to me in a
few weeks from Gary Brown. I will leave no stone unturned in checking all
of the diodes,
caps, transistors etc. before I start getting ready to apply any power.
What I do know is that he 12V supply works, the filaments and pilot lamps
light up when they
should. HV Transformer had an intact secondary. One primary shorted.
When the transformer gets back to me rewound, I plan to start it up on
120V at first, as one
peson suggested and make sure I can get at least 800V or so of HT before
proceeding
further.
Again huge thanks to everyone (including Robb) who has made efforts to
guide me in this
troubleshooting and repair. You guys' knowledge and experience are a huge
help for
somoene looking at this for the first time and pondering what the heck
goes on in this
wonderful box of tricks!
73 from AF4K
Bry
On 2 Feb 2014 at 18:28, Robb Urie wrote:
On 2/2/2014 2:03 PM, Bry Carling wrote:
> Nope. The power switch only sends power to pilot lamps and
filaments on mine. The standby switch energizes relays that apply
primary power up the HV transformer.
Then this amp is certainly not stock...High voltage is applied via
the high voltage rectifier board 81538, there are no relays in the
original design. Perhaps the ham who sold it to you modified it
without either documenting it or failing to tell you. Before
complaining about poor quality transformers from Ten Tec, maybe a
better understanding of exactly what your amp really is would have
been better.
Your original post did state "Only blows the fuse when switched to
operate" caught my attention. I also found that strange, but did
not respond as you seemed to have found the primary shorted. I have
had two 422's, a late one that went "Bang" resulting in a new set of
HV caps and an early model that seems to be working just fine. At
one time, the 422 was a good value, but now at the current price
point I would have to look elsewhere if I was in the market.
Keep us posted when you get your transformer back.
73,
Robb N0RU
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