All things LA2a related

[Scenaria]

well..

I would put in one tube at a time

see if it blows with one tube.. if not then try another.. see if you can narrow it down to one of the tubes.. then I would look around to see if you have short somewhere.

be very careful... as it sounds like you might have a shorted lead...

always always allow time for the caps to discharge.

dont put the T4b in yet...

 

[rove]

well if I turn the unit on now without any tubes it just blows a fuse. I looked around for any shorts, I'll look closer.
any help appreciated.
thanks

 

[CJ]

Are you using slo-blo fuses?
What amps rating?
Check the two diode polarities.
Ohm out filter caps and see what they say.

 

[rove]

I am using 250 volt 500mA slo-blo fuses.
the diode white bands are nearest the front of the chassis.
c7a=7.6k
c7b=12+k
c7c=80k
c7d=250k

thanks!

 

[CJ]

disconnect the red wire going to the front of the 4.7k pwr resistor and plug it in.
check polarity on c7 a-d

 

[rove]

[quote author="CJ"]disconnect the red wire going to the front of the 4.7k pwr resistor and plug it in.
check polarity on c7 a-d[/quote]
there are the two red wires coming from the Power transformer through the diodes, should I disconnect both of them?
thanks.

 

[Scenaria]

nono

what cj is talking about is the lead that goes from the capacitor down to the front of the 4.7k 2watt power resistor

leave the two red leads from the power tranny hooked up

:green:

 

[CJ]

Yeah, what Baby Face Nelson said.
http://www.fbi.gov/libref/historic/famcases/babyface/babyface.htm
:green:

 

[rove]

I just disconnected the + of c7b and blew another fuse, then disconnected the + of c7a (reconnecting the first) blew another fuse.
thanks again for the help.
I get 3 more tries tonight, then back to the fuse shop tomorrow.

 

[CJ]

Please disconnect the red wire.
Thanks.

 

[rove]

[quote author="CJ"]Please disconnect the red wire.
Thanks.[/quote]
I don't know what wire you mean as the "red wire" sorry.

 

[CJ]

OK, never mind.

And disconnect one of the green heater wires on the pwr trans.
Not the one that might be grounded.

 

[rove]

ok, disconnect a heater wire, reconnecting the above link I unsoldered or leaving it disconnected?
then try to power up with the heater wire disconnected?
sorry for any communication failures...

 

[CJ]

Yes, we are seeing if your hetaer circuit has a short.
Actually, before you blow another fuse, you could ohm out the place where the green wires get hooked to, looking for a dead short. Pull the tubes for this test, as they will seem like a dead short to the meter.

 

[Scenaria]

umm

dont power up when you ohm it out

:razz:

 

[rove]

meter shows .4Ω resistance when I measure between the heater wires, power off.

 

[CJ]

Disconnect both green heater wires and fire it.

 

[rove]

[quote author="CJ"]Disconnect both green heater wires and fire it.[/quote]
tried it. blew fuse.

 

[Scenaria]

ok dont take this the wrong way...

but did you remember to put the insulator under the main turret board?

also check to make sure none of the turret mounting screws are touching any of the tube sockets..

 

[rove]

insulator is under the turret board. None of the mounting screws appear to be interfering with anything. there did appear to be a bad solder joint on C7c (neg), I fixed that, reconnected the heater wires, turned it on, blew another fuse. uggh. Got one more fuse tonight...