Info or manual needed. Johnson 2 meter VFO (mobile)

[ke7trp]

I picked up an EF Johnson 2 meter VFO.  ITs small. Only 2 meter.  Has Xtal cable with plug for front of transmitter.  Then we have two wires, white with Red stripe and one white with black stripe. 

Anyone have the manual or information on this unit?   I am going to hook it to the Globe 2 meter am rig and I dont know what voltages its expecting..

C

[WQ9E]

Clark,

Are you sure it doesn't also cover 6 meters?  The only Johnson VHF VFO with which I am familiar is the little one that matches the 6N2 transmitter.  I have one of these and I believe I also have the manual if this is the same VFO that you have found.

[Pete, WA2CWA]

We need a picture and/or model #.

[ke7trp]

Its very rare.  It is very small. Only covers 2 meters.  Someone told me that it was for the mobile they made. 

I have traced the wires down. 

white with red stripe. Goes to big resistor and oa2.  This must be Plate voltage.   My Globe outputs 360. 

White,  Goes to Tube filiments and pilot bulb.  Globe outputs 6.3 AC. 

White with Black stripe,   Goes to Cathode of 6bh6.  Must be a keying line?  Should this be grounded during operation?

Shield.. This goes to the globe case ground pin.

I think I better figure out a resistor for that HV.  The Johnson 6 and 2 mobile VFO says 250 to 300 volts. I have a solid 360 under key. Any ideas as to what or how to lower this?

Sorry for the crappy pictures. I have the thing all apart tracing wires down.  I am wiring the octal socket so this thing plugs in the Globe. 

C

[ke7trp]

It works..  I ended up putting the HV through my Eico resistor box  I turned the dial until I got a solid 148 volts DC at the OA2 under load.. The tube fired off around 200 volts in.  There is already a Big power resistor there so I left it alone.  250 IN, 148 solid at the oa2.    This worked out to be around 7K resistance.  I put this resistor in the transmitter on an unused pin and then updated the manual. I think 360 would have been just to much. It was showing 415 in tune mode. 

Its not very stable on the freq meter but the Power out is rock soldi 20 watts.  I think its going to be good to go once I get all the covers back on. The VFO is apart on the bench. 

Now.. What do I do with the cathode key wire?   Hook it to the dowkey with a Ground return?  The Dowkey keys up in tune and in operate.  The Globe has no relay inside and it has no provisions for keying up this VFO.

Since the B+ is not active in standby. It seems to me, that I can just ground this wire in the VFO and then rely on B+ to start the VFO up. 

Agreed?
C

[ke7trp]

The signal is not strong enough.  Its very hard to find the peak. Its very hard to tune. I replaced the signal cable with a new 2 ft long piece thinking that would help. Its just not enough Drive out of the VFO.

The tube is good. The oa2 is good. If I put a counter on the output of the VFO, the signal is there on the counter. If I plug it into the Globe transmitter, I cant get a good enough peak on the osc meter.

Anyone have any suggestions? Maybe swap the 6BH6 out for another tube with more gain?

C

[WQ9E]

Clark,

The circuit you describe sounds like the 6N2 VFO less the switching for dual bands.  The manual is on Bama and it will be helpful for you.

[ke7trp]

Yeah. I downloaded it last week. It was helpfull. 

I have it up and running.  All voltages check. The VFo outputs 8.222 like I set it for.  Its solid output.  When I remove the Xtal from the globe,  insert the cable to the VFO socket. There simply is no signal.  It wont kick the Globe over. At one point, i had it working but its now wont start the globe to oscilate.

I even changed the series Cap up and down and put a variable in. I cannot get it to lock and stay with the VFO.

Going to walk away from it for a while... and think about what it could be.

C

[ke7trp]

Thanks for your reply..

I tried TWO VFOs. A Globe 6 and 2 and now this Johnson. Both output on 8mhz.  Both show this on the counter. I have an 8.222 xtal. The radio works fine with the xtal.

BOTH vfos do not show any OSC on the meter.. NO rise.  I have changed caps. At one point, I had it working.  But now nothing. I have checked or changed every cap in the VFOs.  I even replaced the cables.

For some reason. These VFos wont drive the old Globe transmitter.

C

[WQ9E]

Clark,

Does your WRL transmitter need any circuit switchover or modification to work with a VFO instead of a crystal?  Generally the cathode RF choke is shorted to convert an oscillator over to buffer/doubler operation.

The cathode keying line in the Johnson VFO must be grounded for operation and also make sure that the "hot" side of the VFO output is fed to the proper side of the crystal socket.   

How long is the output cable from the VFO?  The WRL transmitter may be sensitive to excess capacitance from the cable length.

I use the similar Johnson 6N2 VFO with my 6N2 transmitter and it has no problem driving it.  The 6N2 uses one section of a 6U8 as an oscillator which acts as a buffer/doubler when driven by the VFO.  I have never tried any of the WRL/Globe VHF gear so I don't know anything about the exciter stage of your rig.

[WU2D]

Rodger is hitting the mark on this one - check that stuff out. A crystal oscillator circuit is not a happy and efficient amplifier or multiplier unless you do what he says (set it up for amplifier mode). Alternatively you can drive the P out of it with another stage like a class A amplifier like another 6AU6, 6BH6 or 6AG7 etc... and usually get the stage to multiply effectively.

Mike WU2D

[ke7trp]

I need to scan the schematic so you guys can see this osc.  I have hooked teh VFO up to the transmitter again with my probe on the xtal socket. The VFO is showing 8222 right there at the socket. But I still cant get any OSC rise when tuning. I am sure this is something simple.

There is no switch to VFO mode.

C

[ke7trp]

GUys. Thanks alot for the help.  I am going to work on the thing today.  The Xtal socket is NOT grounded. The left side runs right to the tube pin and the right side goes to a 50 PF cap and then to another tube pin.  I was told this is cathode doubling or something along those lines...

I will look for a resistor!

C

[ke7trp]

I spent some time with it on the bench again.

I set the VFOs output to 8.222 the same as my working Xtal.

I hook the VFO up and attempt to tune the osc. No bump on the needed.  Big bump on the xtal.

I have read the output of the VFO during the tune up. Its there.. 

The LEFT side xtal connection goes to Pin 8-9 on the schematic.  There is a 100K resistor on the schematic. Radio does not have one.

The right side xtal goes to a terminal strip. Then through a 50pf cap to pin 7 of the 5763 tube.

There isa 47K resistor from ground to Pin 7. But that resistor does not appear on the schematic. I jumped it out and the rig stopped working all together. No xtal or vfo.

Maybe I should try adding the 100K back in?  Maybe someone ripped it out..  Its clearly NOT in the radio

C

[Pete, WA2CWA]

Maybe you should review the VFO circuit for the WRL 6 & 2 VFO (compare Johnson VFO to Globe VFO) that was designed to work  with the Hi-Bander.

[ke7trp]

I have the WRL VFO.. It does not work either. 

To review..

The transmitter works FB with the Xtal installed.

The Johnson VFO and the Globe both output on my counter right where I want them.

No Rise in OSC current with either VFO. 

I put the 100K in. No change at all. 

I retuned the slug. I got some output.. about 2 watts with the VFO working.  Counter was bouncing around the area that I need it to be on but not stable.

Anyone have any other ideas here?

Thanks for all the help. I am sure there is something simple that is preventing the VFOs From driving this osc arrangment.

C

[ke7trp]

Thanks for posting the schematic. I will sit down and compare.  Lots of different parts here. ...

C

[ke7trp]

That 6 and 2 is very different.  None of the first half is even close to the hibander schematic. It would be a complete rebuild to get it to function like that. 

C

[WQ9E]

Clark,

When you get a chance, post the schematic of your transmitter (at least the oscillator/buffer/multiplier).

The 6N2 works well but I wouldn't want to rebuild your WRL to match it

[ke7trp]

Yeah.. I am going to have to go buy a new scanner/printer.  Mine crapped out.  Let me take a photo of it real fast.


Try this...

[WQ9E]

Clark,

 
Make sure the hot side of the 6N2 VFO is connected to the side of the crystal socket going to the grid and temporarily short across L1 (use a short piece of wire tack soldered in place).

This should allow the oscillator stage to operate properly as a buffer for the VFO.

[ke7trp]

No change with L1 shorted.  Tuned up the rig with the xtal.  removed Xtal, Put VFO cable into Xtal socket, Shorted L1. No peak. I went across L1s terminals with a wire.  Also tried shorting L1 and the resistor after L1.  No peak on osc. Tuned it full around over and over.  Flipped the Xtal socket around. No change. 

Put xtal back in, Rig tuned right up.

Had Probe of Counter on the xtal socket. The VFO is showing 8.3 right there at the radio. When I unkey the VFo looses B+ and the signal goes away.  VFO appears to be working.  Radio will not show any OSC current with the VFO connected.

Any other ideas?

C

[WQ9E]

Clark,

What does your manual say about the frequency multiplication circuitry-specifically what is the proper frequency input to the first multiplier stage?  Is the VHF 62 doubling in the oscillator stage when it uses a crystal?  What does the manual say about using a VFO for drive?

The VFO should have plenty of drive but if the oscillator stage normally doubles it will be on the wrong frequency.

At this point a scope would also come in very handy.

[ke7trp]

The Xtal is 8.222  This gets me 18 times over.

It works FB with the xtal.  I have the matching Globe 6-2 VFO.  It does not work either. I just dont understand why it wont work. Maybe I need the manual for the Globe VFO... Anyone have it?

C

[ke7trp]

Update..

Plugged the Globe VFO in and tried it out again.

Tuned rig up to full output power with Xtal. 

Put Freq probe on Globe VFO.  Shorted Key jack. It has a stable 8.222 right out.. nice and strong.

Put that into the Globe and BINGO!  I have osc rise.. nice and strong. 

But now I cant get the Buffer knob to tune.. No change in buffer current.. and as a result of that. There is no Final Grid current and no power.

When keyed up, The counter reads 21mhz...   I tuned L1 with no luck.  Shorted L1 and the osc current goes away.

C