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Author Topic: Collins 32S-1 issue  (Read 25374 times)
KH6VP
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« on: September 14, 2015, 02:41:43 AM »

I bought a Collins 32S-1 and have issues with transmitting. When I put it in PTT mode (the VOX gain to the PTT switch position), I can setup the bias to 40ma, but no TX and no more current is drawn, no matter what setting the Tune and Load settings are or the Exciter Tune. Neither change when the emission control it at Tune or Lock Key. I can hear the radio go into TX however (hear the click)

Other settings are as the manual says. Any basic issues I am forgetting here?

I do know about tube radios and already have a KWM-2(which works fine). I also have the 75S-1 and it works fine.

Thanks,
Peter
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WB4SPT
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« Reply #1 on: September 14, 2015, 01:12:56 PM »

Seems like three important things are needed.  
  • grid current (RF drive)
  • Good DC voltages on finals
Good finals

Can you get grid current to peak on the meter?
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N2EY
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« Reply #2 on: September 14, 2015, 01:43:26 PM »

Does it have the crystal pack installed? Or, is it hooked up to a 75S-1?
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KH6VP
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« Reply #3 on: September 15, 2015, 06:21:00 AM »

The power supply is used on the KWM-2 and the KWM works great.

I did not connect the 32S-1 to the 75S-1 using the transceive VFO cables. However, I see there are other cables [jumpers] on the rear connectors. How are these connected?

I can adjust the 40ma Bias current OK.

Nothing happens when I turn the exciter tune or plate knobs.

The guy I bought it from sold it as working.

Thanks,
Peter
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N2EY
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« Reply #4 on: September 15, 2015, 07:02:19 AM »

The power supply is used on the KWM-2 and the KWM works great.

I did not connect the 32S-1 to the 75S-1 using the transceive VFO cables. However, I see there are other cables [jumpers] on the rear connectors. How are these connected?


Read the manuals.

IIRC - and you need to check this - if the transceive cables are not connected, the 32S-1 must have crystals installed. Most do not, because the cables are used.

73 de Jim, N2EY
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KH6VP
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« Reply #5 on: September 15, 2015, 10:52:10 AM »

I have read the manuals. And crystals are installed.
I just tried to tune it. on the 3.6 position, I can tune it, but if I lower the mic gain to decrease the grid current, grid current rises so if I increase the mike gain, grid current lowers. I d have some output; it peaks at 10 watts. A little output on 40 and nothing above.
Is it normal that grid current rises with lower mike gain?
I will now use the 6146 from the kwm-2 to see if there is a difference.
Testing as we speak, so to speak...
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WB4SPT
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« Reply #6 on: September 15, 2015, 11:51:57 AM »

Peter;  what test equip do you have?   O-scope, DMM with 1500 volt DC range?   Do you have another receiver to determine that the driver stage is at the expected  frequency?  (no need for close probing on that test)
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KH6VP
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« Reply #7 on: September 15, 2015, 12:23:53 PM »

I now found out what's going on.
I can push about 50watts out when I am on the 14MHz band and the exciter tuning is almost around 3.4MHz, i.e. when all the slugs are almost completely inserted! No where else. I think the radio needs alignment.
I must read up on alignment or get someone to align it.I have osciloscopes, spectrum analyzers and the like. I just have no time!
Thanks for the help
Peter
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AC2EU
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« Reply #8 on: September 15, 2015, 12:38:35 PM »

I now found out what's going on.
I can push about 50watts out when I am on the 14MHz band and the exciter tuning is almost around 3.4MHz, i.e. when all the slugs are almost completely inserted! No where else. I think the radio needs alignment.
I must read up on alignment or get someone to align it.I have osciloscopes, spectrum analyzers and the like. I just have no time!
Thanks for the help
Peter


Nah, the worst alignment in history could not have slipped that far! You have a failed component somewhere.
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WB4SPT
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« Reply #9 on: September 15, 2015, 01:18:04 PM »

The first mixer puts out around 3MHz.  You may have an issue with the xtal osc or 2nd mixer.  Definately xtals in the box right?  Grin
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KH6VP
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« Reply #10 on: September 15, 2015, 10:57:19 PM »

I will take photos tomorrow and upload them here. Thanks for the all the help!
Maybe its not alignment. As you say, maybe there is a component bad. I did test all the tubes with my tube tester and they all check put fine. I also replace the 6146 finals from the working kwm-2.
If I transceive connect the VFO of the 75S-1 (using the two cables), and the problem is still there (using RECEIVER VFO) then it should remove the VFO as a culprit, right?

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AC2EU
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« Reply #11 on: September 16, 2015, 07:59:59 AM »

I will take photos tomorrow and upload them here. Thanks for the all the help!
Maybe its not alignment. As you say, maybe there is a component bad. I did test all the tubes with my tube tester and they all check put fine. I also replace the 6146 finals from the working kwm-2.
If I transceive connect the VFO of the 75S-1 (using the two cables), and the problem is still there (using RECEIVER VFO) then it should remove the VFO as a culprit, right?



Yes split the problem in two halves with an external VFO if that is an option, VFO vs PA. If the PA works as advertised, then you know it's the VFO area.
There is probably a mixer issue somewhere in the VFO, as mentioned in a previous post. check
See if there is a difference in functionality between USB, LSB and CW modes in the transceiver. That may tell you something about where to look.
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KH6VP
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« Reply #12 on: September 16, 2015, 08:56:07 AM »

Well, I open the unit to see something obvious. I took photos. These are at:







If you look at the last photo, there is a wire that is cut (in the center in front of a resistor). This is white with green band. Does anyone know where it goes? Is it supposed to be cut like that?

Maybe it's the problem.

Thanks,
Peter
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WB4SPT
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« Reply #13 on: September 16, 2015, 09:32:54 AM »

yep,  hard to imagine that's stock.  Its now a 0.1pF cap! The circuit affected is not obvious to me, but is it not feeding a center conductor of a small coax?
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KH6VP
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« Reply #14 on: September 16, 2015, 09:37:07 AM »

Yes, it is the center of a coax. The ground is grounded with the others ground (see it behind the resistor). Hopefully, someone with a 32S-1 will tell me where it goes from their radio's layout.
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