Uniden Pro 640e, NB/ANL problem

Exit_Thirteen · Post by **Exit_Thirteen** » Tuesday 11th Nov 2008, 3:05

Howdy folks, got a nice Uniden Pro 640e that has an NB/ANL problem.

Make: Uniden
Model: Pro 640e
PCB: PB-105AB
PLL: D2824
Mods done: Galaxy "N" kit installed for extra channels, unlocked clarifier, AMC/ALC turned up a bit

Here's the trouble. When I am receiving a station on AM, and I push in my NB/ANL button, the signal becomes distorted. The SSB is unaffected by this, only happens in AM mode. When I have the NB/ANL button out, signals on AM are nice and clear. I got this radio back recently from a friend this way, so this must have happened when he had the radio. Any suggestions as to what the problem may be?

Any help would be most appreciated. Thanks!

-Exit

Rick · Post by **Rick** » Tuesday 11th Nov 2008, 5:50

Try adjusting L2 and check D1, D2 and D3.

Exit_Thirteen · Post by **Exit_Thirteen** » Tuesday 11th Nov 2008, 10:14

Hi Rick, thanks for the quick post!

I checked D1, D2, D3, all good. Adjusting L2 did not help with the scratchy signals on AM, however.

I did clean the NB/ANL button with some contact cleaner to see if the switch was causing the scratchy audio, no change.

-Exit

Rick · Post by **Rick** » Tuesday 11th Nov 2008, 11:30

Please use Post Subject.

What is the voltage at the base for Q3 with NB switched no and off?
What is the voltage at the base, emitter, and collector of Q5 with NB switched no and off?
What is the voltage at the base, emitter, and collector of Q6 with NB switched no and off?

Exit_Thirteen · Post by **Exit_Thirteen** » Wednesday 12th Nov 2008, 2:36

hi Rick, here are the voltages:

Q3, Base
NB off, 0V
NB on, 2.4V

Q5
NB off, B = 0V, C = 0.6V, E = 0V
NB on, B = 0V, C = 0.6V, E = 0V

Q6
NB off, B = 1.0V, C = 0V, E = 6.8V
NB on, B = 1.0V, C = 0V, E = 6.8V

-Exit

Rick · Post by **Rick** » Wednesday 12th Nov 2008, 2:55

Try unsoldering on end of R8 and try the radio to see if the fault still there.

Exit_Thirteen · Post by **Exit_Thirteen** » Wednesday 12th Nov 2008, 3:09

Hi Rick,

I unsoldered one end of R8, no change, fault is still there.

-Exit

Rick · Post by **Rick** » Wednesday 12th Nov 2008, 3:32

Ok the fault is not in NB circuit.

The fault is in the ANL circuit, I should have remembered this circuit is not used in SSB mode.

Check, D16, D17, D18, and C57, It may be D18 is leaking, it probably best to just change all the parts and see what gives.

Exit_Thirteen · Post by **Exit_Thirteen** » Thursday 13th Nov 2008, 1:35

Hi Rick,

C57 was the fault, installed a new capacitor, radio works perfectly. Thank you so much for your time!

-Exit

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