| Author |
Message |
    
Fewb
| | Posted on Thursday, January 09, 2003 - 10:12 pm: | 
|
I have a jb-2000 it lights up but not key up.
any halp. |
2600
| | Posted on Friday, January 10, 2003 - 12:43 am: |
|
Good chance it's 25 or more years old. Everything that goes bad in 25 years on these is expensive. They skipped blowing any air on the underside of the sockets, so solder tends to melt out of the two filament pins on the large tubes. This will often burn the plating off the socket contacts. A socket with burned contacts will then melt the solder out of the pins on a new tube. Lotsa fun. Squeezing a fan in under the tube sockets is a terribly good idea.
The driver tube (if it still has one) is type 8417, the rarest and most expensive tube that is wired to match the driver socket. Every other substitute for it is too wimpy to last in a JimmyBrown 2000.
The big stack of six high-voltage filter capacitors under the chassis left-front are only supposed to last 15 to 20 years, tops. If they are original, expect them to break down.
Does the relay go "click" when you key the radio? It wasn't built with a standby switch. One knob on the front controlled the SSB delay. All the way to the left was for AM, with no unkey delay. Turn it to the right, the delay gets longer. Turn it all the way right, and you get standby. And if yours isn't original, then who knows?
Just watch where you poke inside this monster. The voltage needed to run the "fruit-jar" 3-500Z tubes is genuinely lethal. Even after the cord is pulled out of the wall socket, those high-voltage filter capacitors can store a real wallop. They are supposed to bleed down in a couple of minutes, but never trust your life to a bleeder resistor. Always lay a screwdriver shaft onto the rim of the chassis and touch the tip to EACH tube cap before touching ANYTHING ELSE, AT ALL inside there.
This model contains one odd quirk. The driver tube can't withstand having High Voltage on it until it fully warms up. They installed a relay on the High Voltage, and a thermal delay to control it. When you flip the power switch, there should be no high voltage until a minute or so later. A loud "CRACK" noise from inside announces that the H.V. is turned on and ready to key. If the delay is defective, the relay could be coming on the moment you flip the switch. If the delay is just plain broke, the High Voltage relay may never be getting turned on at all. Until it does, you will hear the relay "click" when you key, but won't show any power at all.
Could turn out to be like "repairing" a '72 Buick. Might turn out to look more like "restore" if it needs tube sockets, tubes, filter caps, relay and a fan or two. Just include that big transformer in your prayers before bedtime. It's genuinely expensive.
73 |
Crafter
| | Posted on Monday, February 10, 2003 - 4:15 am: |
|
After you let it set awhile discharge the caps again. Spent 2 days in the hosp working on mine back in 88 while they tried to get my heart to regulate. Explain that to a doctor at age 22 being hooked to a pacemaker to regulate things But had mine was turned on too! |
Mauldropper508
New member
Username: Mauldropper508
Post Number: 1
Registered: 8-2007
| | Posted on Friday, August 24, 2007 - 11:27 pm: |
|
Eimac tubes melted on the pins Amprex didnt. Guess you now know what z's to buy if you can locate any amprex these days |
Jyd
Advanced Member
Username: Jyd
Post Number: 564
Registered: 11-2001
| | Posted on Tuesday, October 30, 2007 - 11:12 am: |
|
keying transister |
|
