[Top] [All Lists]

Re: [Amps] Titan 425 keying issues

To: Amps Amps <>
Subject: Re: [Amps] Titan 425 keying issues
From: Jim Brown <>
Date: Sun, 15 Jul 2018 10:41:00 -0700
List-post: <>
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.

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 

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

Amps mailing list

Amps mailing list
<Prev in Thread] Current Thread [Next in Thread>