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Old 19th Jul 2020, 11:37 am   #1
davidh1041
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Default KW2000 Transceiver

I am in the process of restoring a KW2000 that I have owned since I was about 16, have replaced all the Hunts capacitors and out of tolerance resistors, rebuilt the PSU and included the mod for the VFO valve heaters. Currently have the filter in bits for cleaning. I have also just acquired a KW2000B, which I intend to give the same treatment.
My question is, I would like to fit the X lock huff and Puff VFO stabilizer kit but unfortunately these are no longer available. Does anyone know of another kit that is available that I can use to further improve these rigs stability? I am not clever enough unfortunately to home construct one from scratch, would need a kit or at least a ready-made PCB. I intend to use the vari-cap diode in the VFO that currently is for IRT.
Thanks in advance for any information.
David
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Old 19th Jul 2020, 1:56 pm   #2
James Duncan
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Default Re: KW2000 Transceiver

Hi.

Have you tried a voltage stabilizer on the dc supply to the VFO, this does help with the slight instability that occurs on most valve VFO's.

Hook a volt meter to the VFO supply and observe to find if the voltage drifts, be patient takes time ,if it does the frequency can also drift.
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Old 19th Jul 2020, 2:03 pm   #3
mickm3for
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Default Re: KW2000 Transceiver

Hi with the heter and ht stable the drift is not realy a issue in my opinion
Info on huf puf circuits http://www.hanssummers.com/huffpuff.html.
The MKRS 80 tranceiver uses one and is horrid to use, the tuning is like a worn slomo drive , they work by sampling the frequency and comparing this with a xtal then ajusting to corect any error, on my 2000b and 2000mk1 having stable heater and ht supplies drift is minimal after around 30 mins i have the circuit for the ht mod, pm me if required, hope this helps Mick
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Old 19th Jul 2020, 3:39 pm   #4
PeterRoberts
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Default Re: KW2000 Transceiver

Hi David,

I've just purchased a kit from ELcon. I'm intending to use it in my FT-101E.

Its not arrived yet, so am unable to comment on how well it works!

The page is mostly in German, but Google Translate is very handy.
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Old 20th Jul 2020, 7:02 am   #5
G3VKM_Roger
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Default Re: KW2000 Transceiver

Hi David,

You will probably find some help here, if you're not already a member:-

https://groups.io/g/KW-Radios/

73

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Old 20th Jul 2020, 5:52 pm   #6
davidh1041
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Default Re: KW2000 Transceiver

Quote:
Originally Posted by James Duncan View Post
Hi.

Have you tried a voltage stabilizer on the dc supply to the VFO, this does help with the slight instability that occurs on most valve VFO's.

Hook a volt meter to the VFO supply and observe to find if the voltage drifts, be patient takes time ,if it does the frequency can also drift.
Thanks for your input James, the rig has an OA2 staberlizer fitted.
David.
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Old 20th Jul 2020, 5:57 pm   #7
davidh1041
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Default Re: KW2000 Transceiver

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Originally Posted by mickm3for View Post
Hi with the heter and ht stable the drift is not realy a issue in my opinion
Info on huf puf circuits http://www.hanssummers.com/huffpuff.html.
The MKRS 80 tranceiver uses one and is horrid to use, the tuning is like a worn slomo drive , they work by sampling the frequency and comparing this with a xtal then ajusting to corect any error, on my 2000b and 2000mk1 having stable heater and ht supplies drift is minimal after around 30 mins i have the circuit for the ht mod, pm me if required, hope this helps Mick
Thanks Mick, some interesting circuits there, will have a close look and think about it. The problem i had with my KW which i used extensively during the 80/90's was i was mainly using it on CW with an "Insect" audio filter, a little drift was a bit more of a problem. But agree after it had been on for about half an hour it did settle down.
Regards David
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Old 20th Jul 2020, 5:58 pm   #8
davidh1041
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Default Re: KW2000 Transceiver

Quote:
Originally Posted by PeterRoberts View Post
Hi David,

I've just purchased a kit from ELcon. I'm intending to use it in my FT-101E.

Its not arrived yet, so am unable to comment on how well it works!

The page is mostly in German, but Google Translate is very handy.
Peter that looks like a nice little device, i would be interested in how you get on once you fit it.
Regards David
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Old 20th Jul 2020, 6:01 pm   #9
davidh1041
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Default Re: KW2000 Transceiver

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Originally Posted by G3VKM_Roger View Post
Hi David,

You will probably find some help here, if you're not already a member:-

https://groups.io/g/KW-Radios/

73

Roger/G3VKM
Thanks for the link Rodger, i am on the KW Yahoo group but not this one, so will subcribe. It's amazing the information and help available on forums like this one!
Regards David
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Old 20th Jul 2020, 9:50 pm   #10
G3VKM_Roger
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Default Re: KW2000 Transceiver

Hi David,

The Yahoo KW_Radios group moved to Groups.io a couple of years ago but all members at that time were migrated along with the files and photos. Yahoo Groups has closed.

73

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Old 20th Jul 2020, 11:33 pm   #11
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Default Re: KW2000 Transceiver

Found this on another site, written by Roger, G3YRO.
"The biggest cause of drift in the KW2000 is the fact that they use a 12AT7 mounted on its side as the VFO . . . on some makes of valve the grid gradually sags more and more, causing the drift. Using the best make of valve (Mullard I seem to remember) reduces the problem a lot! "
I am sorry I cannot remember what I used, had a 2000A a very long time ago.
I think it was a CV type I used and it drastically reduced drift.
Les G4CNH
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Old 21st Jul 2020, 7:11 pm   #12
davidh1041
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Default Re: KW2000 Transceiver

That's interesting Les, when i have finished renovating it i will give that a go. I am currently struggling with the mechanical filter.
Thanks Rodger for the info on the yahoo group. As soon as i clicked on your link it recognised me and i was into the group.
David G0SGT
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Old 22nd Jul 2020, 7:06 pm   #13
Keith
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Default Re: KW2000 Transceiver

Quote:
Originally Posted by Top Cap View Post
Found this on another site, written by Roger, G3YRO.
"The biggest cause of drift in the KW2000 is the fact that they use a 12AT7 mounted on its side as the VFO . . .
The 12AT7 is actually the crystal controlled carrier oscillator so not sure how that is going to drift.

The VFO is a 6U8 (ECF82). I found that stabilising the heater supply on mine improved things somewhat (http://www.tibblestone.com/oldradios/kw2000.htm).
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Old 22nd Jul 2020, 7:21 pm   #14
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Default Re: KW2000 Transceiver

This has got me going now. I have a KW2000B, which I've had for ages, awaiting rebuild.

It's complete, and had already had the D.C. heater mods etc. It a really clean example, it still has the clear protective plastic film over the front panel! Not looking forward to the mechanical filters though.

It's going to have to wait for a bit as I've also a Hammond Tone-wheel organ that's first in the restoration queue.

Good luck with yours, I watch progress with interest.

David.
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Old 23rd Jul 2020, 2:21 am   #15
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Default Re: KW2000 Transceiver

"The VFO is a 6U8 (ECF82)" - Yes that rings a bell, I guess the old grey matter deteriorates with the same ease as the insides of the mechanical filter.
I thought the 12AT7 was not right but bowed to that information as my memories had faded so much. Looking at my CV register the nearest equivalent is the CV5065.
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Old 23rd Jul 2020, 8:57 am   #16
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Default Re: KW2000 Transceiver

The stability of my KW2000a improved greatly after I changed the out of tolerance resistors and caps within the VFO compartment. Not easy to get to. I did the filament mod and don't think I need to add a Huff & Puff. It does drift a bit for the first half hour but settles down. In qsos with anyone using a modern rig they will probably notice some drift.
I remember reading that the 6U8 was an improvement on the ECF82. Although listed as equivalent they are not necessarily identical. Perhaps someone can clarify this. I can't say that i noticed any difference myself though.
Don m5aky
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Old 23rd Jul 2020, 4:48 pm   #17
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Default Re: KW2000 Transceiver

I recall reading somewhere that the 6U8A (the controlled-warm-up version) was significantly better in VFO applications than the original 6U8.

Whether an ECF82 is a 6U8 or a 6U8A I wouldn;t like to say!
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Old 23rd Jul 2020, 4:49 pm   #18
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Default Re: KW2000 Transceiver

Great and helpful website Keith thank you.I have an A +B awaiting the bench.6U8 ia American and ECF82 Mullard and to quote "sensibly equivalent".
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Old 18th Sep 2020, 8:18 pm   #19
davidh1041
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Default Re: KW2000 Transceiver

Just an update on the KW. I removed the VFO box, replaced two black Hunts that had just about disintegrated, checked the resistors and mechanical stability of the coil and associated capacitors. Also I have replaced the ECF82 with a PCF802 which was designed of course for tv line oscillators, and has a much more stable construction. I simply replaced the LM7805 with a LM7808 in the heater supply mod. to provide 9 volts the PCF802 needs. (I have a BC212 in the earth leg of the LM7808 to gain a volt] The Xtal oscillator valve is running from the existing 12 volt heater rail via a 20 ohm resistor. The transceiver now settles down much quicker and no noticeable drift after 30 minutes.
I think I will not be adding a huff puff stabiliser, as I am more than happy with it as it is now. Thank you for all your interest and help.
David
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Old 19th Sep 2020, 1:44 am   #20
G8UWM-MildMartin
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Default Re: KW2000 Transceiver

Thanks for the update.
I'll bear the PCF802 & regulator mod. in mind (sure I've got one somewhere) when I eventually get round to working on the KW2000A I bought in 1994 and just replaced the Hunts that had fallen to bits at the time, and subsequently robbed it of the perfect RCA 6146Bs it had that upset the heater current balance. I now have a pair of QV06-20s that can go in and be neutralised. But it has light rust and I wonder whether the mechanical filter might still be OK.
One thing I remember from then is it had some Colomor 6BA6/EF93 valves that weren't really because they failed test owing to a slightly different pinout because they were USSR types, but I forget the details. I must remember to look into that to see whether it matters.
Martin.
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