Bias mystery solved

[N3DRB The Derb]

I could never get Yeasu #1 to throw down enough bias on the cheep tubes. I had to crank the pot to the stop to even get 40 ma, much less 60. I knew this was trouble brewing so when I went in there to put the AM filter board in place I decided to do some snooping. I'd rather replace crap before it burns up.

here are the culprits. The real offender is the little guy on the left. It claims it's a capacitor, but it's more like a 140K resistor with a chip on it's shoulder. When you see rubber bulging out of the bottom so bad that the cap cant touch the board it's soldered to, time to play change dat cap.

So putting in a major cap order now to put in some stock for repairs on both #1 and #2. Anyone got any favorite sources for radial lytics in the 250 volt range? I'm gonna buy about 20 of them. 

 

[w3jn]

I gots a bunch, I can send 'em to you

[N3DRB The Derb]

too late, already ordered em offa ebay 

Hey, what are those black disks you sent me? I cant remember for the life of me what they are for.  I only remember something about 1 ohm cold or something like that. 

[WD8BIL]

Damn ur gud Derb !

[w3jn]

Negative temp coefficient thermister.  They're good inrush current limiters.  1 ohm cold then when they heat up they're like .01 ohms.  They get hot so mount 'em somehwere they're not gonna melt anything.  I got a box of 'em and thought they'd be good for your leenyar.  Those are good for about 20 amps IIRC.

[N3DRB The Derb]

so mount em in series both hot and neutral lines or just hot? I had it wired up and then memory kicked in and I said you better ask about them things.

Thanks bud. Yeah I dont F around when I need parts, I get em. Gonna lay in a ton o stock of both caps and resistors.

I got 2 real 275 watt tips today for my D550 gun and damn does that thing solder big stuff nice.

[w3jn]

You could put one in each lead, see what happens.  Prolly better to use just one in series with the hot, I dunno.  I use one of those selfsame NTCs between the primary windings in my GPT-750 - just replaces the jumper for 220 operation.  You don't have that option with your Gonset though.

[Todd, KA1KAQ]

I bought a kit of those things off da bay last year, plastic container full of values. Still haven't used any, but I gots 'em just in case(literally). Interesting idea on using them as the 220 jumper on your TMC, Johnny. Bet I could figure that out on ol #89, too. 

Derb, I had bias problems last February with my audio deck. Recapped the entire thing and replaced a naughty 6B4G driver, works slick since. I've become a stronger believer in replacing old caps than anyone ever thought possible. Got some 60s-era REL gear with those newer gray and blue caps in places, in some cases the innards are now outards. Bet you'll be very happy when they are gone.

[N3DRB The Derb]

my rule on thumb on lytics is over 100 volts and/or 20 years old, toss em. It's just not worth it. I need to check the main filters on them too. Those are expensive buggers but after it's done, you'll never have to worry again about loud bangy crapouts. The lower solid state voltage level units go bad too of course, but the tube voltage level units have a hell of a lot more stress on them.

I cant believe how many peoplez don't get that filter caps need to be changed on a 50 year old radio and discarded. Its like getting a 50 year old car out of a barn and expecting to be able to drive it around and have the brakes be good. Lots still think they only need to be changed when the radio is buzzing or humming.

the load all these transsexual sex change caps (now preoperative resistors)    puts on transformers is pretty great when you start multiplying the additional current drawn X number of bad actors.