Final Amplifier Build...

I've been building an amplifier for a friend, the last few weeks. This is the last one I'm building, as it's getting harder to get parts for valve amps. 

It's based around a GI-46B triode linear amplifier for 11m and 10m.

There's still quite a bit of work to do on it, before it's able to produce any power out. 

More photos

Nice work Ian, I'm following with interest.

73 Gary.

C.T. Admin.

Hello Ian,

Fantastic work. I look forward to seeing the finished results.

73s John.

I've done most of the metal work and just to finish off the wiring. The wiring always gives me the biggest headache, as I forget how I did it on previous occasions.

Nice work Ian and really good to see.  


For some unexplained reason I half expected to witness an off the shelf 'standardised' amplifier build but really impressed noticing your handiwork and spotting perf. board as well as handmade coils & chokes. Awesome stuff!

(Nitty-gritty builds seem less common nowadays and I know I don't exclaim "I've built a phone" when I plug the USB lead in to charge the damn thing or download software to/from it. )

Really makes your other amps stand out with such construction dedication and I wish you well with this one also.

Great stuff and makes me go all "Ham-gooey." (Love seeing 'home-brew'.)


All the best,
Victor

Coming along nicely, Ian.

Victor wrote:

Nice work Ian and really good to see.  


For some unexplained reason I half expected to witness an off the shelf 'standardised' amplifier build but really impressed noticing your handiwork and spotting perf. board as well as handmade coils & chokes. Awesome stuff!

(Nitty-gritty builds seem less common nowadays and I know I don't exclaim "I've built a phone" when I plug the USB lead in to charge the damn thing or download software to/from it. )

Really makes your other amps stand out with such construction dedication and I wish you well with this one also.

Great stuff and makes me go all "Ham-gooey." (Love seeing 'home-brew'.)


All the best,
Victor

Much of it was trial and error, from others builds, plus advice from others. 

There's no ready made metal cabinets to be had, this side of the Atlantic (at a realistic price), hence the need to fabricate my own.

A bit more of the RF deck complete. The anode current meter was DOA, from China. I'm waiting on a replacement from England.

The construction looks fantastic, Ian.

Don't it just John.

I'm still drooling at the sight of a door knob capacitor!

Victor wrote:

Don't it just John.

I'm still drooling at the sight of a door knob capacitor!

Just to satisfy your fetish!   

A "slim Russian model" will do it for me every time.


Joking aside Ian, not only very well done with your construction abilities and technical know-how but also in your resourcefulness at obtaining such parts. 

Victor wrote:

A "slim Russian model" will do it for me every time.


Joking aside Ian, not only very well done with your construction abilities and technical know-how but also in your resourcefulness at obtaining such parts. 

It's not the neatest build, but functional.  Ebay and other places are good for hunting for parts, etc.

Nice build, what sort of power are we looking at ?

kilomike wrote:

Nice build, what sort of power are we looking at ?

About 500W or so.

I've been having problems with the build, specifically the GI-46B valve is very power hungry and the modified microwave oven transformer and voltage double circuit, aren't up to the job.  It gets very hot, far more than the GI-7BT valve does.

Because of this and some problems with the output tank coil, I'm retrofitting a GI-6B valve into the amplifier.  I've got a GI-6B valve with no anode heat sink, so I'll just attach the heat sink from the GI-46B on it.  They have the same thread size for the anode, so no problems with that.  In fact, it'll be more efficient that the usual GI-6B heat sink, as it has more surface area.

The GI-6B has a smaller diameter for the main body, as compared to the GI-46B, so I'll need to fix up a new support place for the base.  Electrically, the valves should be the same.

The build it complete, but I'm not happy as there's too much heat being produced. I'm going to have to look at the cooling system again.



That's 2.68kV on the anode of the valve!

Nice work, Ian. I am sure you will get the heating issues sorted.

73s John.

Great stuff Ian. On to the next project!!!

73's Gary.

This is the replacement fan I have installed. It's noisy, but works really well. I'm going to take soundproofing measures.

I've repurposed similar fans pulled from containers of failed IBM 3588-F5A tape drives. Not quite so juice hungry at 1.23A. I haven't noticed them particularly noisy, but then I work in a very noisy environment. I had one on top my monitor last summer directed at my forehead to keep me cool  If you ever need a replacement, or build another, tap me up as I am bound to have some spare I could send over. Size is 120x120mm



Have you thought of putting a thermal sensor switch in line with the fan so that it's not on continuous, which would make it quieter some of the time. Probably only cost £1-2.

SangueG wrote:

I've repurposed similar fans pulled from containers of failed IBM 3588-F5A tape drives. Not quite so juice hungry at 1.23A. I haven't noticed them particularly noisy, but then I work in a very noisy environment. I had one on top my monitor last summer directed at my forehead to keep me cool  If you ever need a replacement, or build another, tap me up as I am bound to have some spare I could send over. Size is 120x120mm



Have you thought of putting a thermal sensor switch in line with the fan so that it's not on continuous, which would make it quieter some of the time. Probably only cost £1-2.

It'll need to keep running all the time, due to the heat build up. The old microwave oven transformer runs warm, as does the valve heater...

I brought one of these fans home a few days ago with the intention to use it to cool some equipment. I was surprised how loud it sounded in my home, it really showed me how loud my workplace environment is. I found running it at about half speed made it sound almost silent but still pulled enough warm air away from the item.

Have been looking over your project photos again and have to say you have some great skills in metal work and electronics. Antennas aside, my electronic project efforts look not much better than when I was in primary school. Here's my voltage stepdown circuit for the fan 



Your project looks fantastic inside and out. Your friend is very very lucky. I do hope they credit you when they use it on air by by saying they use an amplifier made by MM0IMC.

SangueG wrote:

I brought one of these fans home a few days ago with the intention to use it to cool some equipment. I was surprised how loud it sounded in my home, it really showed me how loud my workplace environment is. I found running it at about half speed made it sound almost silent but still pulled enough warm air away from the item.

Have been looking over your project photos again and have to say you have some great skills in metal work and electronics. Antennas aside, my electronic project efforts look not much better than when I was in primary school. Here's my voltage stepdown circuit for the fan 



Your project looks fantastic inside and out. Your friend is very very lucky. I do hope they credit you when they use it on air by by saying they use an amplifier made by MM0IMC.

Nothing wrong with your attempt, as it looks neater than mine!

I think ever homebrew linear amplifier should have a name, so I've called this one The Flymo due to the fan noise!