uniden washington

[kaos513]

ok r29 was the issue with the meter works now as for the am carrier still a no go.

 

[OldTech03]

Well? I don't know if I'm looking at the right schems but r29 on the schems I'm using should not affect the meter circuit maybe the volume maybe?
Anyway, you need to establish if there is any RF being generated in any of the stages from the xmit mixer onto the driver. If there is rf there it should show easly on a scope or even on a bench radio with a wire stuck in the back anything please show us the RF. LOL

 

[kaos513]

Ok will report soon

 

[Handy Andy]

What is the voltage to Driver and Final - IN AM mode - at TP7 or TP8?

Else you may have a TX transistor (aka MB3756 Toggling issue)

How's the RX/TX light - works ok? TR35 goes to the CB PA switch off of the MB3756..

Since you have SSB mode - if you posted differently - correct me, but you also get "mod" you did not say if you watched the RF meter or the Mod meter - again correct me if I'm wrong.

But what this seems to be is if you lost the AM yet SSB works - TP7 and TP8 IN SSB MODE would still show full battery supply - in AM it drops to about 4.5 volts - as much as 5.6 volts...

Now what I find that fails in this is the 1N60 D54(correction on the previous post) samples the AM power carrier and makes it adjustable thru a voltage divider circuit R195, D54 into Pre-driver of Darlington TR42 - and other half of divider uses R194, D63, R228 and C173 - with OFFSET from VR10 (8VTX regulated)

​

The graphic posted shows the AM and SSB MODE selector and how it bypasses the AM Regulator TR41 and TR42 and also includes the Divider circuit that OVER 130% MODULATION!!! as done in a previous thread - @ExitThirteen used to show asymmetry.

You cant do this on a regulated AM regulator like a Galaxy or Uniden that do not use a divider like the above...

Unfortunately - I blew it up - but the thread still exists...at your leisure to read...

IF you build it, they will come...

 

[kaos513]

do not hear nothing on the other radio when I key up and whistle to mic

 

[kaos513]

Tx/Rx light works perfect ,front buttons work as the meter as well.am &ssb has no audio as well as no output power

 

[kaos513]

Tp8 &9 have 13vdc

 

[OldTech03]

At the risk of sounding like I don't know what the H I'm talking about I'm going to guess and hope that the measurement on TP7 and TP8 (TP9?) was taken in the SSB mode as it should only be around 6 VDC in the AM mode unless of course there is a problem with the measurements that we could not know about.

 

[OldTech03]

do not hear nothing on the other radio when I key up and whistle to mic

Do you see any signal from the Washington on the other radio? modulated or not

REPEAT:
At the risk of sounding like I don't know what the H I'm talking about I'm going to guess and hope that the measurement on TP7 and TP8 (TP9?) was taken in the SSB mode as it should only be around 6 VDC in the AM mode unless of course there is a problem with the measurements that we could not know about.

 

[nomadradio]

The transmitter is a series of stages, starting with a mixer. It puts together RF at 7.8 MHz from the carrier crystal with 34 MHz RF from the radio's PLL section. Your 27 MHz signal comes out of this mixer, and into L28. If this part of the radio works, a very weak signal may be present. Too weak to jump a few feet into another radio.

The purpose of using a spare coax jumper as a "sniffing" antenna is to hold it an inch or so above the transmit sections of the radio. A signal too weak to travel out of the radio's cabinet to the other radio can be detected this way.

If you can hear nothing with the second radio, this means that your transmit signal is not being generated in the first place, even at a low level.

No point in looking at the power-amplifier stages if your transmit signal is not being fed into them in the first place.

73

 

[OldTech03]

The transmitter is a series of stages, starting with a mixer. It puts together RF at 7.8 MHz from the carrier crystal with 34 MHz RF from the radio's PLL section. Your 27 MHz signal comes out of this mixer, and into L28. If this part of the radio works, a very weak signal may be present. Too weak to jump a few feet into another radio.

The purpose of using a spare coax jumper as a "sniffing" antenna is to hold it an inch or so above the transmit sections of the radio. A signal too weak to travel out of the radio's cabinet to the other radio can be detected this way.

If you can hear nothing with the second radio, this means that your transmit signal is not being generated in the first place, even at a low level.

No point in looking at the power-amplifier stages if your transmit signal is not being fed into them in the first place.

73

Yes, I suggested the sniffer wire somewhere in one of my posts but not as elegantly as you have so it doesn't hurt to be redundant.

 

[kaos513]

Well I can undust my signal tracer and put it to work

 

[kaos513]

At the risk of sounding like I don't know what the H I'm talking about I'm going to guess and hope that the measurement on TP7 and TP8 (TP9?) was taken in the SSB mode as it should only be around 6 VDC in the AM mode unless of course there is a problem with the measurements that we could not know about.

Removed the green and purple wire then I probed tp7 and tp8 they measure around 13 vdc without keying up

 

[Handy Andy]

Removed the green and purple wire then I probed tp7 and tp8 they measure around 13 vdc without keying up

In AM mode - what are those voltages?

 

[Handy Andy]

Here's what I'm working with - so if there is a discrepancy - it is due to the TP designation...


VR 12 handles MOD - so if you are NOT getting any RF at those voltages check Mode switch or Pre-Driver - and as we progress - looks like Pre-driver is out of commission...