I own three of these amps, and had to troubleshoot them several times.
To make that easier, I drew up the schematic in AutoCad and printed it
to several pdf files that are on my website. k9yc.com/publish.htm
Except for the tubes, all of the circuitry is garden variety discrete
transistors, diodes, and resistors that can be replaced by readily
available parts. The only troubleshooting tool I needed was a Simpson
260 to check the semiconductors. You'll need to remove the boards to
troubleshoot them. Check EVERY semiconductor -- when one blows, the
fault often takes out others, including a power resistor that's part of
the bias circuit.
As to "won't key up" -- make sure that you're keying it properly. The
keying logic in this amp positively prevents "hot keying" by monitoring
the position of the vacuum relay. The transceiver MUST have enough
keying delay time set that (after PTT from the transceiver) the relay
pulls in before the transceiver sends RF. My experience has been that 8
msec is enough, and this is the default for many (most?) rigs. I've
never tried less.
73, Jim K9YC
On 7/12/2018 9:45 AM, martin dulaney wrote:
Hello everyone I am hoping that some one on here can help me out!
recently purchased a used titan 425 ran great the first week ! although the
meter lights were out .
28ma 1300-1500 out opened it up the bulbs were 12 volt in series replaced them
closed the cover back up
powered it back up meters light up it wont key up??
tried removing the bulbs no joy replaced Q1 and Q2 on the bias board still no
joy
checked all of the relays K5/K4/K3/K6 they all close when powered directly bias
on terminal 85 on the bias board reads 8.5 volts all of the time.
relays K5 changes state when you switch from standby to operate
28 volt source on pin 7 from ps reads good
meter reads approx 2.4 kv when in ep??
at a loss here hopefully some of you gentlemen have some clue as I sure don't
would also be interested in purchasing a used but good bias control board
Thanks And 73's Martin KN4DXD
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