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RE: The delightful EICO HF12

Posted by Bambi B (A) on February 11, 2008 at 11:29:32

In Reply to: RE: The delightful EICO HF12 posted by izzbo1@yahoo.com on February 11, 2008 at 10:01:50:

izzbo1,

I noticed in your reply you mention plugging the HF-12 in but "not getting sound" and at the bottom of your post mentioning not seeing the ON-OFF switch. With that combination of comments, you may have not turned it on, in which case you will not have done any harm and can try again a bit more carefully.

It occurred to me that if you have any lights in your house that are on dimmers, you could buy a screw-in adapter that converts the socket to add an electrical outlet- you've seen these in garages and cellars, plug the HF-12 into that and bring the dimmer up slowly, watching the brightness of the bulb- start and hold it it 1 minute very dim light, 1 min. low light, 1 minute medium, and so on until full brightness, then let it run and think about it for an hour to warm up before trying it. This may be using the full voltage all along, but with variable amperage, but seems might offer a "softer" start without a variable transformer. Before doing this, clean the tube pins with 400 grit sandpaper- and be sure and get all the grit off, and be sure and have the speaker connected as well. Of course to get sound, you'll need to connect a source and probably a CD player is best- trying it with phono or tuner offer too many distractions about the source.

The ON-OFF on these is the strangest one I know in audio- instead of the usual POWER/VOLUME combination, on the HF-12, the right knob marked TREBLE is also the power switch! This means that whenever you turn it on, you also have to set the TREBLE around to the position you like.

You might find a vintage site or perhaps our Vintage Aslyum where someone can email you a *.PDF of the manual- in any event, I would strongly recommend getting the manual and schematic to have the whole picture.

You're lucky to have the original tubes- the Mullard 12AX7s and EL84 are among the sought after ones and you might pay $40-50 each for the 12AX7s if they are strong. I forgot about the 6CA4. This is also known as an EZ81 and is the rectifier that changes the AC current to DC. I'm very fond of amplifiers with tube rectifiers- the Dynaco ST-70 being a famous one, using a GZ34. The "Holland" marking probably means it's an Amperex- also among the best makers. By the way, all of the tubes in your HF-12 can be dated quite exactly by deciphering the tiny etched codes on the glass- you have to look carefully to notice these. The 12AX7s will show something like: I65 4B2. When you clean the tube pins, make a note of these codes.

If the light dimmer power up would work, clean the pins and jacks, and have the speaker connected, I'd be tempted to try it before sending it for repair. Of course, there'a a reason the console was parted out while leaving the HF-12 and it may be the HF-12 had problems. Remember too that 40-50 year old speaker drivers may be shot and with a typical guitar use need to be in good shape. For the initial tries, you may want to use a speaker you know to be working- but not a really valuable one,or you may be hearing speaker problems instead of amplifer problems.

It looks like a fun, inexpensive way to ease into tube audio. If it works, but doesn't appeal as a guitar amp, buy a EICO, Scott, or Fisher mono tube tuner, and something like a Dual 1019 turntable and the HF-12 could be the centre of an appealing office or bedroom system. Many people think mono is a useless, obsolete techonology, but in many cases, mono is quieter, and more open and dynamic than stereo. I have a Scott 330D mono tube tuner (1959) and this makes among the best FM I've ever heard!

Cheers,

Bambi B

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