Gonset 201 MKIV

[WA4JK]

Anyone have any experience with one of these? I'm tired of fixing the AL-811 all of the time and I have a chance at one of these. The owner says it has 811's in it, I thought they had 572b's in the MKIV. How well do they hold up to AM with 15W of drive. I would expect about 125W carrier max and that is all I plan on running. Thanks

[W4AAB]

AJ4W near Cullman, AL has( or had) one of these on ssb a number of years ago. The 572B's will work fine, plus they are zero-bias(Gonset used -4.5 vdc bias on their GSB-101 on the 811A's).

[WQ9E]

The Mark IV would have originally come with 572B tubes but maybe they were replaced along the way with cheaper 811A tubes.

I have a 201Mk4 and I have had no problems with it although I think others have reported bandswitch problems.  Mine is paired up with a HT-32 and SX-101A.  It shouldn't have any problem at 125 watts output but 572B tubes would be preferable.

[WD8BIL]

What problems are you having with the AL-811? Is it something going to 572Bs might help resolve?

Anyway, the original 201 used 811As. They switched to 572Bs in the MK3.
The manual in .pdf is attached

[K3ZS]

I have a GSB-101, with four good 811's.    On AM, at the recommended 275 mA input current, the rated carrier output is 175W.   It is good to increase the loading to this value even if the output power drops, so you get the full PEP value of the AM output.

[WA4JK]

The Al-811 keeps having one problem after another. Now I thing one of the sockets has the grid cap and resister open issue. I have not fixed it yet but it took out the tube in that socket. I get a arc from the bottom of the socket area. This is the second issue with it. It took out three taylor 572b's the first time. That aint cheep.
On the Gonset I was worried when the owner said it had 811's instaed of 572b's. The plate voltage might be a bit high for the 811's. I would also have to reduced the current values as well. How do you tell the difference between the MKIV and the other 201's which use 811's from the front?

[The Slab Bacon]

I dont know much about the Mk4s, But I redid a MK2 for Derb. It was quite a strapping little amp when I got done with it!!

It had 811As, I changed it to 572Bs and got 200w carrier power out with no problems running out of headroom. I could just get 1000w flat out down hill, balls to the wall out in CW mode. So it could do 250 carrier with enough headroom for 100% mod peaks. He ran it at 200w for the extra headroom for the audio peaks.

If the MK4 is anything like the MK2, be very careful with and gentle on the bandswitch. they are undersized and do not handle the circulating currents very well. They will fry out if you look at them wrong. I also had some instability problems. The fil choke is just too small and there isn't physically much room for anything bigger. You need to make sure the end that goes to the fil winding is bypassed 6 ways from Sunday. Also make sure the resistors in the parasitic chokes are good or they WILL go parasitic on you. Also the filament winding didnt have a center tap and would produce a noticable hum in AM (or CW) mode. The "artificial center tap" mod fixed that.

Once I cured the problems and design faults with it, it was a really neet smokin little amp!! Well worth the work. And they are pretty compact and easy to move around.

[WA4JK]

Wasn't planning on running full tilt boogie, but 125-150w carrier would be nice. How about tripping a MKIV with a FT-102? does the 201 require a mod to pull in a relay??

[The Slab Bacon]

Wasn't planning on running full tilt boogie, but 125-150w carrier would be nice. How about tripping a MKIV with a FT-102? does the 201 require a mod to pull in a relay??

It was SUPPOSED to be RF sensing but didnt work very well with the 10 or 15w drive from the FT-101 that it was paired up with. so I added another relay to fire it off with the amp keying contacts on the 101 and used the original relay to swing the antenna.

It was real happy running at 200w not a problem.

[Ralph W3GL]

   The 102 has tubes in the output as I recall...  That will be fine for the
   Gonset GSB 101/201 whatever amps...

   It is not good with a solid state driver as there is NO input matching circuit
   in that beast.  The late plastic no tune outputs want to see a 50 ohm load.

   With the HV used in there, you need 4.5 or so volts bias with 811A's but
   572's run just fine with zero bias at 2100 Vdc...

[WA4JK]

Well it looks like the owner stuck 811's in a markIV and says it works fine. That won't last long with 2100v on the 811 non biased. It is in Canada and would cost way to much to ship and I would only give him what one without tubes would be worth. Not much and I don't want to embaress him.

[K3ZS]

I use an external autotuner with my fully solid state ricebox to match it to the input of my GSB-101.   It is necessary to drive the amp to full output on 40 and 80 meters.    Something I didn't need with my sweep tube output transceiver.

[WQ9E]

The Gonset 201 amps are very heavy and need to be packed very well for shipment.  I saw one at a hamfest and the transformer had caved in part of the chassis from a hard drop when it was shipped.  I have serviced a few Tektronix 500 series scopes that had the same shipping damage.  Tek scopes survive it pretty well but I don't believe the Gonset amp has the same robust build.

Hopefully the converter did add operating bias when the 811A tubes were installed.  Otherwise the tubes probably look like those in a CB amp I saw at a hamfest.  It used a quad of 811A tubes and all the little horizontal fins were drooping from heat.

[WD5JKO]

The gain of these AMPS is about 10db, so 15w drive gives ~ 150W, and with 811A's that is a little HOT for Linear Amp AM.

I have a GSB210 MKIV also. These are worthy amps with a few issues. Mine was shipped, and packed well, but even so the HV bleeder resistor cracked in two.

One issue is as Bacon pointed out, the filaments grounded on one side cause 60 hz cathode modulation, ~ 10% or so. Disconnect that ground and Make an artificial center tap is what I did with a 10 ohm (or thereabouts) power rheostat did the deed. Thinking back, maybe I could have just used a 6.3V C.T. filament transformer, about 1 Amp or more, using it as a center tapped choke. Leave the 115 vac winding not connected.

On my unit, I have ~ 5:1 SWR on 80m, and under 2:1 on the higher bands. Maybe Bacon is right, and the filament choke is low on inductance for 80m. Using an 'L-Network' cures the 80m SWR problem.

Mine has 572B's, and at 200W am this thing loafs along, where old buzzard transmissions don't seem to make it get too hot. I used it in the AM rally (the first one) driven by a Gonset G76. I needed a 5 DB pad since the G76 had too much power. I was on all bands 80-15 at 200W AM during the Rally.

This AMP is a workhorse!

One thing though, looking at AM with a trapezoid pattern, with a near perfect excitation, the AMP output shows a little curvature. Switching over to my 8877 based AMP, the trapezoid on the AMP output matches the exciter input.

Expect that you will need to Re-Cap the HV power supply.

Jim
WD5JKO

[WA4JK]

The best I can discern from the owner is he just stuck 811's in and tested it on 80m just to see if it worked. Not a good omen, it is in canada and based on the tubes needing to be replaced and the cost of shipping I passed. Seems like a good AM 150-200w amp with a few issues which can be overcome. Thanks for the comments guys. It's good to have a source for discussion.

[Steve - K4HX]

Check the fests and for sale ads. You should be able to find one closer to home. Keep an eye out for the Dentron Clipperton L. It also used four 572Bs and covered 160 meters.

[WA4JK]

The dentron is one I have no knowledge of. Might be ok I'll look at the comments for it.

[WQ9E]

I have a Clipperton L and it works OK but I don't think the power supply is as rugged as the Gonset.  It could just be the difference between old and new iron.  160 meter coverage is nice and the Clipperton L is compact.  I haven't tried mine on AM (yet).

[WD5JKO]

The Gonset power supply uses a FW CT type rectification (solid state) with a choke input filter on the negative lead. The choke is huge, and the voltage regulation is really good. Most competing amps use a FW voltage doubler instead which in my opinion are cheaper to produce, but the regulation suffers unless the transformer is really stout and you use over sized wire to the power panel. This is why the Gonset weighs as if it filled with lead.

Jim
WD5JKO

[WA4JK]

Wish I could find one of the 201's sounds like it would fit my needs just fine.