The Friendly 12bar Blues Guitar Forum

Thought I should give some more details of my little Harmony tube amp. This one started out as a Harmony 400A. The "A" designates this as the upscale model of the 400. Instead of just a volume knob, the 400A also has a tone knob! Many Harmonys, Kays, Airlines, Silvertones, and others were made by Lectrolabs. Though they were different on the outside, they were very similar internally. The cheap ones used radio tubes that were easily obtainable then but are uncommon now. Because they were cheap many of them did not have power or isolation transformers, which keep your strings and fingers away from wall voltages. Without an isolation transformer you had to make sure your two-prong plug was inserted into the wall socket correctly. If you do that you are protected by a capacitor and resistor (which if either shorts out will send wall voltage to your fingers). This capacitor has been nick-named the "Death Cap".

While trying to bring this Harmony to life I attempted installing an isolation transformer but met with mixed results. When it worked it had a weird insect-like buzz. Mostly I couldn't get it to work at all. When I finally gave up and pulled the iso-tranny the amp settled down to a clear, quiet tone with very little clean head room but a very sweet, gentle distortion. I also replaced the tubes and all capacitors and removed one input jack and the pilot light which was broken anyway.

Wrapping it up is a 12" Rola (1966) Speaker and a Bitmo "Ten"uator, which is a small 10watt attenuator in kit form that's meant for Valve Juniors or other low output tube amps. All this was put into a pine Tweed Deluxe Clone cab which is really too classy for the little amp.

Here are some pics: The pic of the amp internals shows the old capacitors (brown cylinders) and the old filter capacitors (big triple bundle with white powder indicating a cap leak).

So that's it! Sad to say my practice area (the cave) flooded during a nasty downpour lastnight. Nothing important ruined. Just clean up I don't have time for. Life marches on...

Love the pine cab.
I used to have an old ('63) Alamo amp with a 10 inch speaker that had a very similar tube compliment. Gave it to buddy when I moved out to NM, but I still have the matching "63 reverb unit. Some of the cheap vintage gear is actually very cool. I have a late '50's Supro TV front amp, maybe 5 watts, that is great, and only cost about $150.

oneeyedslide wrote:If you do that you are protected by a capacitor and resistor (which if either shorts out will send wall voltage to your fingers). This capacitor has been nick-named the "Death Cap".

I would never play such a thing. Didn't Keith Relf from the Yardbird die this way?

But it sure looks and sounds great

I think I'd be too much of a to risk it too.

Then if I did play something that sounded that good and didn't know about the danger would I go back to it again .... I'm not so sure - d'you know, maybe I would.

At first, i do not now this sow sorry when i say someting stupid.

But is it not posseble to cuver the top? then the widowmaker will not make widows any more

Aint she sweet :)

I still have the Bitmo 10Uator to

12bar wrote:

oneeyedslide wrote:If you do that you are protected by a capacitor and resistor (which if either shorts out will send wall voltage to your fingers). This capacitor has been nick-named the "Death Cap".

I would never play such a thing. Didn't Keith Relf from the Yardbird die this way?

But it sure looks and sounds great

Yes, Keith Relf did die due to an improper grounding of his amp.

I have a late '40's/early 50's Alamo Amp3 that would fall into this category with a Jensen P8R field coil speaker. I've added a grounded three prong cord to hopefully prevent any grounding issues. Here's a very poor quality picture of the amp:

Yeah, the three prong plug takes care of one of the big issues. If power becomes shorted to the chassis (and consequently the strings and bridge of your guitar) it will hopefully trip a modern circuit breaker or blow the fuse in your amp before it harms you. Most of these early cheap little tube amps didn't even have a fuse! The old US type two prong plug could sometimes be inserted into a wall socket backwards which would simply power up your strings. Playing on a concrete basement or garage floor barefoot once would make you think about changing that plug to three prong right away! Harp players would really suffer! To make thing worse, if a tavern owner had wired just one socket backwards and you plugged into it, bzzzzt! A lot of venues probably still have shady wiring.

Another improvement is to change that "Death cap" from an electrolytic type to a more bullet-proof ceramic type. I'm no amp expert, but I do know that the better sounding capacitors also have a definite life-span. I'm pretty sure some of the other types last much longer, maybe even indefinitely.

I read somewhere that Kieth Relf was ill at the time of his death. I'm sure his case was not the only one. I know I've read about musicians being electrocuted onstage. There are a lot of variables that could bear on this type of situation. I have also seen people lick their finger and stick it into a light socket to see if it was hot! Don't let somebody grab ahold of you while they're doing this. I have experienced the string thing with a faulty amp myself a long time ago ('70s) and I really DON'T like the sensation. And it's not easy to let go for some reason.

At any rate it's a dangerous electrical situation, but you can minimize the risks to some extent if you are aware of them. I don't recommend anyone playing one of these. On the other hand I'd rather play it than ride a roller coaster!

Hey Bindboy! Looks like your bandmate Deaconblues may have ended up with your old Alamo! Sweet old amps! The TV front Supro must be wild!

2WheelOfBlues, It would help if I could keep the widows in there, 'specially when one might be my wif!

VikingBlues wrote:Then if I did play something that sounded that good and didn't know about the danger would I go back to it again .... I'm not so sure - d'you know, maybe I would.

Honest! I worry about it too! I'm just weak!

Thanks folks. Interesting discussion!

Hey Bindboy! Looks like your bandmate Deaconblues may have ended up with your old Alamo! Sweet old amps! The TV front Supro must be wild!

Different era Alamo from Bb's. From the build/design of the reverb unit, Bb's was a sixties era Alamo.

DeaconBlues wrote:

Hey Bindboy! Looks like your bandmate Deaconblues may have ended up with your old Alamo! Sweet old amps! The TV front Supro must be wild!

Different era Alamo from Bb's. From the build/design of the reverb unit, Bb's was a sixties era Alamo.

Yup... a '63.

I know. I'm just a troublemaker!