Kriss 200B what relay?

[Jimbo165]

I have a Kriss 200B amplifer the amp works but quite regular the relay after keying stays in keyed position and i have to switch to standby to get it off. I would replace relay but cannot find what type to replace it with. Here is what is written on side of it.
MILW. relay
100T DPDT
5a 2.5k
Any help will be appreciated.

 

[nomadradio]

The description of "stays keyed" can still mean two things.

Does the relay go "click" when you unkey the radio?

If the receiver's channel noise fails to return after hearing that "CLICK", this would suggest a relay with bad or dirty contact points.

But if what you mean is that it WON'T go "click" when you unkey, this suggests that the keying tube has gone bad, and won't shut off the relay's coil current.

Pretty sure the keying tube is type 6BQ5.

There is a resistor from pin 3 of the keying tube that goes to ground. The diagram doesn't show the resistance value. My educated guess is 470 ohms, but I don't know what it's supposed to be. If this resistor is a carbon-composition type, the resistance value can fall with age. If the resistance gets low enough, this could prevent the tube from shutting down properly when you unkey the radio.

73

 

[midnight special]

i had a amp do that to me and i changed the length of the jumper between amp and radio and problem went away,,,,

 

[BlowinSmoke]

Yup, you need to determine in the relay is staying on after you unkey the radio, but if what you say that if you turn the amp off the relay recovers then it is indeed remaining energized and that would make the problem in the keying tube circuit.

 

[Jimbo165]

nomamdradio I have changed and tested tube it's ok . The relay stays down does not go back up no click. Thanks to you i checked and It had a 1k resister and I replaced it and amp works no stick but only if radio deadkey is kept at 4 watt going into amp otherwise amp will not key. If I put 470 ohm in will key at 2 1/2 but problem comes back i may try one in middle maybe will work. This is the second tuber I have ran into that with that problem has to have 4 watt deadkey. Well at least for now it is working but a lot of radios do not have a 4 watt deadkey so amp will not work with them . I still would like to find out what relay it has and I would replace it to see if that would help. Thank You Again.

 

[BJ radionut]

That electrolytic cap across the relay coil...could be bad also or has changed value...that might affect the action also. Might be one of those by-pass caps leaking voltage off the center tap of the transformer.

 

[Jimbo165]

I put a 680 ohm resistor in place of 1k and it keys up down to a 2 1/2 watt deadkey now and seems to be working better i also replaced relay spring with one a little stiffer. Thanks for the info about the capacitor i will look at that also.

 

[nomadradio]

Be careful turning the radio's carrier down too low on that amplifier.

The tubes have no fixed bias on them at all. Sounds backwards, but the radio's carrier serves to control the tubes' plate current. Turn it too low, and the tubes will overheat.

Bad things tend to happen when they do.

If you put a SWR meter and coax jumper between the radio and this amplifier, you will see that the radio is driving into a fairly high SWR when the amplifier is keyed.

When this amplifier was designed, most base radios used tubes. A tube final is more tolerant of high SWR than solid-state finals tend to be.

Installing remedies for the high input SWR, adding fixed bias and making the keying circuit more sensitive is doable, but not simple.

And you won't find a handy "how-to" posted on the net that I have found.

These old amplifers are cool, but incredibly primitive.

Have fun, but watch the tubes to see that they don't "cherry" and overheat.

73