first attempt at gutshots, Harmony H-306-A

[212Mavguy]

This is a rescue amp bought by emptying out my wallet, somewhere between 89-91 bucks fell out and it was mine. Was brought out of a basement where it sat unused for 10-15 years. Initial fireup revealed a lot of crackle and low volume, but the strong hint of sweet, very warm almost dark, very fat basic tone was there in spades. It's only the second amp I have ever attempted to tweak.

Shot pics in daylight outside on a cheap cell phone, hit <ctrl +> a few times to magnify the one back baffle shot, contains the schematic and parts list.

Yanked the old power tubes' cathode bypass cap and replaced with a relatively new one that had a couple hundred hours use in another amp, stuck in a coupling cap from a silverface champ to replace the exploded brown one. For giggles replaced another .015 coupling cap with a .010 before the pics, later that part was removed and replaced with a k40 at original values.

After the pics were taken, all the .015/400 originals were replaced with same values in Russian k40 PIO's, and the .022/600's were replaced by similar value k42 "greenie" PIO's. I left the original ceramic caps, on the grids in V1 and in the trem/power section.

The amp still retains all of its original behaviors and basic tone set, it's quite a bit louder, but MUCH more detail, harmonic content and musical sound. This is the first amp I have had with bias modulated style trem, I love the way it sounds. This circuit is very, very special IMHO. The compression and sustain in clean tones is unusually good. Maybe has something to do with the cheesy, small output tranny and tube rectified power supply. I yanked out the stock '61 Jensen p12r (would be pleased to see it go away for a decent $$) and replaced it with an original cone Altec 600b from the late 40's early 50's.

Am going to have to sell 3-5 amps out of my collection, this amp works so well in a small to medium sized room. Fave way to play is guitar>Hilton active volume pedal, DOD 70's vintage eq/boost pedal. Unlimited sustain on tap with that setup, and the sounds of that trem just hanging bar after bar for someone to float their leadwork over...flamethower single note lead tones are very D-clone like in capability of sustain, even clean, and when pushed can coax some very D-style note flipping sustain notes, the first even order harmonic often prevails an octave up, and this is a PP amp! Have never experienced such a forgiving, sweet sounding amp on stage before. it responds and sounds like a 3000 dollar boutique amp now. Besides the parts upgrade, I replaced every single tube with VOS glass from my collection, strongly prefer the response and tones using a 5v4 instead of a 5y3 for the rec tube, tighter overall and more musical, more mids, besides the "easier on tubes' slow warmup" compared to 5y3.

Next thing I have to do is learn how to record clips and post'em. I'm gonna suffer on that one, am very self conscious recording myself.

Thanks to what I am learning here and Merlin's book, not quite so afraid to try to redo a simple amp anymore.

Thanks all of you here for your shared knowledge!

[xtian]

Very good!

How about some glamour shots of the front and controls?

[212Mavguy]

Sure!

Was going for the hardcore porn shots. Will post the day I shoot 'em.

[Diablo1]

Does anyone know who built this amp for Harmony?
Lectrolab perhaps?
Are the transformers labeled with a manufacturer's name?
The reason I ask is that I have an old amp from 1961 with similar components and building method, and I'm trying to verify who built it.

[Jack Hester]

Does anyone know who built this amp for Harmony?
Lectrolab perhaps?

Could have been Valco.

[Diablo1]

A little more googling turns out that Lectrolab did build the Harmony H-306A, and is identical to the Lectrolab R-600B.

http://lectrolab.wordpress.com/lectrolab-models/r600/

I have a very unique Capitol amp, that also appears to be built by Lectrolab, but I find zero reference to it anywhere on the web. So, if anyone has any info at all on any models of Capitol amps, I'd love to see it posted.

[IMG:640:480]http://i51.tinypic.com/30mvbxs.jpg[/img]
[IMG:640:480]http://i53.tinypic.com/1zwnamg.jpg[/img]
[IMG1200]http://i55.tinypic.com/2z4emis.jpg[/img]

[Structo]

Cool looking amp.

How does it sound?

[Diablo1]

The Capitol sounds great, after I recapped it and replaced some dodgy resistors. It is a stereo amp with each of the output transformers connected to its own Jensen C12R. It has four 7591 output tubes with cathode bias, and you can select half output power (single OT) or full power power (two OTs). It also has a great sounding bias tremolo. I'm fairly certain that it was built by Lectrolab, but the circuit is unique to this model as far as I can tell. No other Lectrolab amps use the 7591 tube.

[212Mavguy]

That is one cool amp you have! And thanks for figuring out who made these!

I have another Harmony on the way from the 'bay, should arrive by next Wednesday, an H-420 1/15 combo, Jensen ceramic, first cousin of the Supro Thunderbolt. Has a treb and bass knob instead of a single tone knob.

[Diablo1]

That is one cool amp you have! And thanks for figuring out who made these!

I have another Harmony on the way from the 'bay, should arrive by next Wednesday, an H-420 1/15 combo, Jensen ceramic, first cousin of the Supro Thunderbolt. Has a treb and bass knob instead of a single tone knob.

Yes, a lot of folks say the H-420 is a Valco built amp, who built the Supro amps. Seems that Chicago used to crank out a lot of amps in the 1950s-60s. A lot of the manufacturers of parts were located here too, like transformers and speakers.