New 160 meter GS-35B shack amplifier..

[VK3ZL]

Well, I started on this new amplifier last Monday..I will take progress pics of this project as it takes shape..I had all the components on hand so I am able to get right into it...These first four pictures are the partial assembled case and most of the major RF output components..I have a metal work plumbing shop in Hamilton 30 miles East of here..Run by a couple of tradesmen they make air condition ducting, plumbing and water tanks and most metal work fabrications...I get them to cut all my panels from aluminum these days as they have the right machinery to do a professional job..Each case costs me about $50 all up..

I bring all the panels home and assemble an amplifier case using 12mm aluminum angle, copious pop rivets and heaps of patience..I cut all major holes for fans, meters, capacitors etc before final assembly...I etch all the internal panels in a caustic soda bath which gives them a neat silky finish which looks good and is easy to clean of finger marks etc..One must be careful not to scratch the surface..I don't have a large enough container to etch the main U shaped case frame..

The rest of the pics show the Pi network components for the RF deck..I hand make the coil using 12 gauge hardened copper wire which is polished then given a few coats of clear lacquer to prevent tarnish..This inductor is 23 micro henries and I will have to take off 2 or 3 turns once I set the network up..The vacuum variable capacitor is a new one purchased from Ukraine, $105..This is 250pf-5kv..The yellow doorknob is a 330pf 20kv shunt..I am using a salvaged 800pf air variable loading cap from an old Heathkit and this is shunted with a Russian 2200pf 6kv doorknob..The coaxial relay for the output is a 75 ohm Russian unit...These relays cost $25 from Ukraine and will withstand over 2kw at VHF..

Last two pics are the GS-35B Russian triode..This weighs 6 pounds, has a 1500 watt anode dissipation and 26 watt grid dissipation...I milled the grid mounting socket from a block of 1/2 inch aluminum plate and turned the hole for the tube on my lathe.Note the step in the socket where the tube grid fits...The tube grid is a fine fit into the socket and held in place with two "keepers"..

That's all to date...I will post another few progress pics tomorrow evening...As usual I am enjoying this job even though I do occasionally issue a few profanities when something isn't right...

Bob..VK3ZL..

[KK4AMI]

Well, I started on this new amplifier last Monday..I will take progress pics of this project as it takes shape..I had all the components on hand so I am able to get right into it...These first four pictures are the partial assembled case and most of the major RF output components..I have a metal work plumbing shop in Hamilton 30 miles East of here..Run by a couple of tradesmen they make air condition ducting, plumbing and water tanks and most metal work fabrications...I get them to cut all my panels from aluminum these days as they have the right machinery to do a professional job..Each case costs me about $50 all up..

Between all the metal work and rose gardening, you must not have an open patch of skin on your hands that isn't scars.

I bring all the panels home and assemble an amplifier case using 12mm aluminum angle, copious pop rivets and heaps of patience..I cut all major holes for fans, meters, capacitors etc before final assembly...I etch all the internal panels in a caustic soda bath which gives them a neat silky finish which looks good and is easy to clean of finger marks etc..One must be careful not to scratch the surface..I don't have a large enough container to etch the main U shaped case frame..

The rest of the pics show the Pi network components for the RF deck..I hand make the coil using 12 gauge hardened copper wire which is polished then given a few coats of clear lacquer to prevent tarnish..This inductor is 23 micro henries and I will have to take off 2 or 3 turns once I set the network up..The vacuum variable capacitor is a new one purchased from Ukraine, $105..This is 250pf-5kv..The yellow doorknob is a 330pf 20kv shunt..I am using a salvaged 800pf air variable loading cap from an old Heathkit and this is shunted with a Russian 2200pf 6kv doorknob..The coaxial relay for the output is a 75 ohm Russian unit...These relays cost $25 from Ukraine and will withstand over 2kw at VHF..

Last two pics are the GS-35B Russian triode..This weighs 6 pounds, has a 1500 watt anode dissipation and 26 watt grid dissipation...I milled the grid mounting socket from a block of 1/2 inch aluminum plate and turned the hole for the tube on my lathe.Note the step in the socket where the tube grid fits...The tube grid is a fine fit into the socket and held in place with two "keepers"..

That's all to date...I will post another few progress pics tomorrow evening...As usual I am enjoying this job even though I do occasionally issue a few profanities when something isn't right...

Bob..VK3ZL..

Between all the high voltage, metal work and rose gardening, you must not have an open patch of skin on your hands that isn't scars.

[K7SGJ]

I'm anxious to see the finished unit. If you ever want to hear how it sounds on the air, just send it to me.

[kb2vxa]

Nice driver stage, I can't wait to see the final.

[VK3ZL]

Well, got a little more done today..I etched up some simple circuit boards for the Bias cut off and Bias board protection..Also a simple Glitch resistor board that goes into the HT line and a Step Start resistor board..Pics show the finished boards..

I also completed the installation of the Pi output network..It all fits snuggly and is resonant through the band..I am just making the amplifier front panel..This takes time and patience..The layout has to be functional and presentable to look at..Also the top and bottom aluminum trims, 12mm square, has to be attached with a 2mm spacing at the top and bottom to accommodate the flush fitting covers..

I have had a few emails asking how I fit the 12mm aluminum angle..I took a pic of one corner while I was working..In this case the angle has to fit 2mm below the sides of the box so that the top cover is flush when fitted..I pre drill the box then cut the angle to size and using small clamps drill and fasten the angle to the inside..I cut all the angle with a hacksaw in the vice and trim it to an exact fit using a file..Works every time, or nearly..:chin:

BTW the fan is a 240 volt all metal 6 inch Papst rated at 290cfm..I like these particular fans as the metal blades are heavy and don't lose speed under load.. This produces more than enough air to cool this tube even at 1800 watts output..I must measure the back pressure..I have a manometer in a drawer somewhere..

Bob..VK3ZL..

[mw0uzo]

Looks great, keep up the updates :)

[K7SGJ]

Well, got a little more done today..I etched up some simple circuit boards for the Bias cut off and Bias board protection..Also a simple Glitch resistor board that goes into the HT line and a Step Start resistor board..Pics show the finished boards..

I also completed the installation of the Pi output network..It all fits snuggly and is resonant through the band..I am just making the amplifier front panel..This takes time and patience..The layout has to be functional and presentable to look at..Also the top and bottom aluminum trims, 12mm square, has to be attached with a 2mm spacing at the top and bottom to accommodate the flush fitting covers..

I have had a few emails asking how I fit the 12mm aluminum angle..I took a pic of one corner while I was working..In this case the angle has to fit 2mm below the sides of the box so that the top cover is flush when fitted..I pre drill the box then cut the angle to size and using small clamps drill and fasten the angle to the inside..I cut all the angle with a hacksaw in the vice and trim it to an exact fit using a file..Works every time, or nearly..:chin:

BTW the fan is a 240 volt all metal 6 inch Papst rated at 290cfm..I like these particular fans as the metal blades are heavy and don't lose speed under load.. This produces more than enough air to cool this tube even at 1800 watts output..I must measure the back pressure..I have a manometer in a drawer somewhere..

Bob..VK3ZL..


Looks great, keep up the updates :)


You two made me feel so guilty with all this home brew, design, building, and ham radio stuff in general, that I got inspired to build something. So, today, I built a fuse tester that runs on 110 volts. The problem is I can't seem to get the fuses out of the test circuit fast enough. I guess it really doesn't matter much as I can't see shit from all the bright flashes, anyway.

[mw0uzo]

You two made me feel so guilty with all this home brew, design, building, and ham radio stuff in general, that I got inspired to build something. So, today, I built a fuse tester that runs on 110 volts. The problem is I can't seem to get the fuses out of the test circuit fast enough. I guess it really doesn't matter much as I can't see shit from all the bright flashes, anyway.

Heh.

I can recommend this should you want to build something
http://www.radio-kits.co.uk/mkars80page.html
Great kit, good price, works very well. The huff-puff VFO stabiliser works properly too, so no drifting around. I do all my 80m stuff on it either barefoot or connected to the amp. Get the case and knob options for a complete kit and also this hand mic, rewiring the inside to suit. :)
http://www.ebay.co.uk/itm/Hand-Shoulder-Mic-Speaker-for-Yaesu-Radio-VXF1-VXT10-VXT20-/270968520741?pt=UK_Mobile_Phones_Communication_Rad io_Parts_Accessories&hash=item3f16fb8025

Don't connect 110V to it though ;)

[VK3ZL]

Saturday..I have been on this job for 6 days now..I did my calculations for the tank output circuit yesterday and made up a new coil...Plate resistance will be in the vicinity of 1500-1800 ohms...This requires a coil around 14uh to 17uh for a circuit Q of 12..I always find that the calculated formula to actual operating conditions varies and proper adjustment of the Pi network can be finalised under power...However it will be within the ballpark..I spent most of yesterday fabricating the amplifier front panel and gave it the final coats of paint last night...I used Metallic Charcoal on this job..It has a fine mica fleck and looks quite good...I lettered up the panel this morning and gave it two coats of finishing lacquer then placed the meters and switches etc..

I am now working on the Cathode compartment and will have it completed tomorrow...Then I will be able to start on the wiring up..

Only 3 pics today..My photography isn't all that good...Two of the completed front panel and the completed Pi network with 17uh coil..

Bob..VK3ZL..

[VK3ZL]

Sunday....I worked on the Cathode compartment today..This has a Pi input network, filament choke and Bias feed choke..The Pi input has a Q of 2 and is adjustable with a slug tuned coil for 1-1 drive vswr..I use a simple 24 volt cradle relay for changeover directly connected to the input coax connector...The toroidal filament transformer delivers 12.6 volts...It is a bit large for the job, 8 amps where I only need 4 amps but it's one I had on hand...The HT passes through the Cathode compartment via ceramic and Delrin feedthrough's...The WW resistor is a 30 watt 22 ohm Glitch resistor in the HT line to protect the HT supply in case of tube flash over..

I am now to the wiring up stage and will work on this over the next couple of days..I have the rectifier stack for the HT completed ready to install.. So not much more to do...

Pics are the Cathode compartment..

Bob''VK3ZL..

[VK3ZL]

Friday...I had a busy week and just got back to the 160 meter amplifier...I wired the front panel in today and completed testing all amplifier functions...Everything switches on and works correctly....The wiring didn't turn out as tidy as I would have liked but it will do the job..

Pics of the front sub panel show from left side, the simple relay/resistor step start...The relay is a 240 volt 40 amp contact single pole single throw unit and a 50ohm 50 watt aluminum clad resistor...I always mount the resistor on standoffs to keep it clear of the chassis in case of an internal short...These resistors usually ooze out the internals when they blow up..

Next from the step start is the bias cutoff resistor and relay...The relay works from the 24 volt relay supply..Then we have the relay 24 vdc relay supply, a simple 240 volt 20 volt transformer and diode bridge..
The far right is the W4ZT bias board...I put the board control potentiometer on the front panel which allows me to bias the tube from full cutoff to class B linear mode...

The meters are 1.5 amp anode current and a 500ma grid current meter..Pic shows the completed front panel wired into the amplifier..For Tune and Load shaft bushes I use the insides of old potentiometers..Simple and cheap..

The HT transformer tells it's own story..I had some of these custom built by Jeff at Harbach in the USA..This unit is a Peter Dahl 2000vac @ 1 amp CCS 50cps for Australian mains...It weighs 53 pounds and takes up 25% of the inside room of the amplifier..I will install it along with the Bridge rectifier pack over the weekend..This will bring the amplifier weight to 75 pounds...Pretty heavy for a simple desk top amplifier..I have to turn up four aluminum legs for the amplifier and fit the to-p cover...The cover will have a Teflon chimney that fits over the GS-35B cooler to duct the air from the amplifier...

I will probably tune the amplifier up next week...I will try and take some pics of the amp running into my Bird load...

Bob..VK3ZL.

[WA7PRC]

It looks good, Bob. Q: Doesn't the GS-35b want to see more HT than your transformer will supply?

I've been s-l-o-w-l-y accumulating parts for my own GS-35b 160m amplifier. I fabricated the W4ZT tube "socket". I recently finished rewinding my plate transformer and am nearly ready to start the PS build.

vy 73,
Bryan WA7PRC

[VK3ZL]

Gidday Brian..I usually run 3500vdc on the 31 and 35B tubes...However I wanted to use up this spare transformer....I will only be running 1kw output and CW only...The whole amplifier will be loafing along at that rate...In my experience the GS-35B tube gets around 55% efficiency properly set up...I have seen statements for 60% but I am sceptical about that...For a $120 tube the 31 and 35B tubes are excellent value....I have never bothered to see what maximum output these tubes will give but in my water cooled 160 meter 35B amp 1800 watts carrier was easily obtained with 3500 volts on the anode...The spec sheet figure on gain is pretty correct although I find on 2 meters and 432 the gain drops off to around 10-12db..So it takes more driving power on 2 and 70cm to realise good output...

I always mount my socket flush with the chassis and seal both the cathode and anode compartments..I use a small fan under the tube in the cathode compartment and evacuate the air through vent holes in the side of the chassis...The anode side is sealed and the air from the big Papst fan evacuates through the tube cooler and a Teflon chimney on the top cover...I have never used parasitic suppressors with these Russian triodes and they show no sign of instability..My engineering has always been guess work but so far no problems.. BTW once the amplifier top cover is in placed the fan noise is very minimal.

I am just in the finishing stages of this amplifier today so I will start RF testing next week...

73..Bob..VK3ZL..

[koØm]

It looks good, Bob. Q: Doesn't the GS-35b want to see more HT than your transformer will supply?

I've been s-l-o-w-l-y accumulating parts for my own GS-35b 160m amplifier. I fabricated the W4ZT tube "socket". I recently finished rewinding my plate transformer and am nearly ready to start the PS build.

vy 73,
Bryan WA7PRC

http://i111.photobucket.com/albums/n150/Paws264/2010/amp-2.jpg (http://s111.photobucket.com/user/Paws264/media/2010/amp-2.jpg.html)

YES!

I ran 4500 VDC under load. I used dual W4ZT bias boards, setting the idle current at 200 milliamps per tube.

.

[koØm]

This is my Transformer, I wired the input for 110 VAC but fed it 234 VAC, the output of which, I ran into a voltage doubler circuit.

http://i111.photobucket.com/albums/n150/Paws264/IMG_20110828_173907.jpg (http://s111.photobucket.com/user/Paws264/media/IMG_20110828_173907.jpg.html).

.

[koØm]

This is a picture of the RF Deck

http://i111.photobucket.com/albums/n150/Paws264/2010/october011-1.jpg (http://s111.photobucket.com/user/Paws264/media/2010/october011-1.jpg.html)

.

[WA7PRC]

Thanks for the replies. Two x GS-35b is more than I'll be running. My 45# rewound xfmr (http://www.tinyurl.com/wa7prc-transformer) looks like this:

http://farm9.staticflickr.com/8530/8647045424_5cdde6990f.jpg http://farm9.staticflickr.com/8121/8640970087_4356b27fd6.jpg

It was a fun project within a project. The donor was a salvaged (free) unit from a medical electronics power supply. It was meant to operate worldwide on 100/120/200/240V @ 50/60Hz. It uses a split bobbin, ensuring very low leakage. I found polyimide (Kapton™) wire on eBay and NMN333 down the road in Oregon. A local transformer rewinder was gracious and vacuum impregnated it for me free gratis. I should be able to pull at least 3A from the secondary (6Ω DCR).

The RF deck will be enclosed in a Heath SB-220 outer case. I have knobs, switches and meters from an SB-220. Yes, it's going to be Heathkit green. It's the law. :yes: :mrgreen:

vy 73,
Bryan WA7PRC

[koØm]

Ugly as hell, but had no problem delivering 60% of 4500 VDC @ 2.0 amps. (Watts = Voltage multiplied by Current) continuous.

http://i111.photobucket.com/albums/n150/Paws264/2010/DCP01016.jpg (http://s111.photobucket.com/user/Paws264/media/2010/DCP01016.jpg.html)

.

[koØm]

GS-35b toobs glow when you put the juice to them

http://i111.photobucket.com/albums/n150/Paws264/th_video-2011-01-13-15-34-28_o.jpg (http://i111.photobucket.com/albums/n150/Paws264/video-2011-01-13-15-34-28_o.mp4)

.

[koØm]

I could never quite get the grasp of simplicity or "neatness"; my "Elmer (W8ERG-SK)" told me to, "Always build a pay day in the job."


http://i111.photobucket.com/albums/n150/Paws264/th_video--16_o.jpg (http://i111.photobucket.com/albums/n150/Paws264/video--16_o.mp4)

Yes, it is not pretty but......Click on the pic to see it work.


.

[koØm]

With the "Proceeds" from that job, I started another amp in January of 2011 but, due to "The Slings and Arrow of outrageous fortune" and the up's and down's of life, it still just a shell. I am just starting to be able to wrap my mind around the idea of finishing this project.

I managed to "salvage" the Pi Network from a Drake L4-b that a operator damaged; the only option was to turn the L4-b into a single band amplifier because of the burnt band switch.

I found that by "indexing" the contacts on the band switch, I could put the switch back in service but only on four bands; I "discovered" this after trying to get the "Stock Taps" on the L4-b coil to tune properly within the Amateur bands when coupled with the GS-35b. Than was a "No-Go" from the start, nothing short of "bumping my head into a brick wall" could compare. The project sat idle for the last 18 months until last month when I tore the Output network out, dumped the 40 and 80 meter coil and re taped the coil for service between 10 meters and 20 meters in 4 steps.

I am working with a limited amount of resources, I don't have access to a Break or Sheet Metal Shear so, a few Greenlee Chassis punches, some Hole Saws, a Nibbler Tool, Files, and Hand drills are all I have to do metal work so, "Pretty" has a very low function in this equation. My electrical instruments consist of a 1960's Eico GDO, an original MFJ 259 Signal Analyzer, a Capacitance meter and various DVM's; I don't have an Inductance meter. I'm building on a shoe string using various surplus chassis and scrap box parts.

This is the third GS-35b amp in the evolution of my amp building.

.

[VK3ZL]

Hi again....I have had a busy week and have just got back into the workshop..HT transformer installed and switched on..All works as it should..I will try and get time to fire it up with RF over the weekend...Here are a couple more pics of the completed job...Actually that's not quite correct, Once I have completed the RF tests I will spray paint the amplifier sides and top cover..I can tell you this, this amp is too heavy for me to lift..I will need help to bring it inside the house to my shack once it is complete..

BTW I have ordered a new batch of Toroidal HT transformers including a 1450 volt @ 1.5 amps unit to replace the Peter Dahl transformer in this amplifier..This will give 3700vdc peak and around 3500vdc under load..My transformer orders take around a month to arrive after ordering..


Bob..VK3ZL..

[W3WN]

I could never quite get the grasp of simplicity or "neatness"; my "Elmer (W8ERG-SK)" told me to, "Always build a pay day in the job."
< snip >He told you to always build a candy bar into the job?

[VK3ZL]

Ok, I have completed the initial tuning up of the 160 meter amplifier this morning..With the existing HT transformer the results are about what I expected...The HT under a 750ma load is around 2600vdc..Output power average with 50 watts of drive is a tad under 1kw so the efficiency is around 55%...Once I put a new HT transformer and boost the HT to 3600vdc the amplifier will become much more efficient..I put 70 watts in and power out was just on 1600 watts output but as I only want to run on 1kw CW I know I have plenty of reserve power..

I must thank Kelli for helping me with a calculation I was trying to get my tired old brain around..My mathematical abilities are no longer working properly and I easily confuse myself with figures..

I now only have to spray paint the top cover and sides of the amplifier and that job is complete for now until I get the higher voltage transformer..

A couple more pics of the amplifier meters running 1600 watts output and the little 706 with 50 watts of drive and a Daiwa vswr meter showing about 900 watts output...The Daiwa meter has been properly calibrated against a Bird...I have a bird but no HF high power slugs...Must buy some one day...

All for now and I am happy...

73..Bob..VK3ZL..

[VK3ZL]

I have just ordered a pair of HT Toroidal transformers for this amplifier...Each transformer is 1350vac @ 1.5 amps..I will stack these with the primaries in parallel and series the secondaries into a bridge rectifier...This will give me an HT around 3.8kv...I have these transformers custom made in China...Cost each is around $150 and $150 shipping for the pair....Probably have to wait about 6 weeks for them..Meanwhile I have removed the Dahl transformer and installed a new 4.5kv rectifier pack using 20 6A10 rec diodes and 10 450 volt 470mfd caps...That is a pretty potent supply with lots of joules..I just have to sit back and wait now and be patient..

Meanwhile I am giving my shack a good spring clean...Coming into winter I have a nice open fireplace to keep the shack warm..I am also about to fire up 40 meters...Not a super station but with the old 751A and the re built 40 meter amplifier into the phased verticals I should have a good signal into the US,
I need to build up a proper phasing system for that antenna so that I can work short and long path..

I am now back on 160 meters every night from my sunset..I am usually listening on 1.824.5 CW...I work most of my regular US contacts through the evenings and if the band is really open many other US and VE stations who don't have big antennas...I am often the subject of a pileup and can work 20-30 contacts over an hour...It is always a pleasure to give stations their first VK on Topband....If any of you get up before sunrise and give me a yell via email etc I will be only too happy to try a call...I still havn't had an "Islander" on Topband..

Cheers...Bob..VK3ZL..

[W3WN]

Bob,

With your permission, I'd like to turn your posts & photos into an article for my club newsletter. (Might not be this month's though). Or if you don't mind doing more of a writeup, that would be good as well.

I think it's important to showcase efforts like yours, as so many have the mindset that "it can't be done" -- yet there you are, doing it.

[VK3ZL]

Bob,

With your permission, I'd like to turn your posts & photos into an article for my club newsletter. (Might not be this month's though). Or if you don't mind doing more of a writeup, that would be good as well.

I think it's important to showcase efforts like yours, as so many have the mindset that "it can't be done" -- yet there you are, doing it.

Sure Ron....Let me know if you need more detail...In fact my methods are very basic..The most difficult part is fabricating the amplifier case...Most of the rest is patience..

Bob..VK3ZL..

[VK3ZL]

Gidday all..Well I completed the 160 meter amplifier at last with the installation of two 1350 volt @1.5 amp HT Toroids..I had to modify the step start to accommodate the switch on inrush current though...I am using a big National 240 volt 40 amp relay here with an 80 ohm 60 watt WW resistor..The lights still blink when I switch it on but there is a discernible time delay click on the relay as the rectifier stack charges up so I think it is probably adequate.There is 50mfd in the capacitor bank..I measured the HT peak without a load and it comes in at 3825 vdc..That's as high as i want around here thanks very much..

I have completed the final coats of paint on the top cover and amplifier sides and I am currently getting the shack tidied up ready for the new amplifier..Only one pic of the completed amplifier..

73..Bob VK3ZL..

[mw0uzo]

Looks great, as always :agree:

[PA5COR]

Yep, works of art they are ;)