My new Hammond H-112 & tips requested

[Waterloo]

Hi all - this is my first time posting but I've been reading at OrganForum for awhile. There are two questions at the end and I'd appreciate any input people have.

I recently picked up an H-112 after a lot of searching and waiting for the right deal to come along. Musically, I'm more interested in classical than blues, but my main interest is to just play around with tones & colours & dense harmony while using 10 fingers & 2 feet.

So why did I choose an H100?
- no/less foldback (when compared with B3)
- stereo knee-level speakers (I fell in love with knee-level stereo with my first organ, a Galanti F-40)
- the extra drawbars (more tonal options)
- the price (mine was $100. $100!!!!)
- ease of adding a Leslie later

What don't I like about the H?
- 25-note pedalboard (I'd have preferred an E's AGO pedalboard, but E has other disadvantages)
- potentially, getting it to work properly...

I'm no expert or electrician, but I've spent some time rooting around and here's the organ's current condition:
- all drawbars & keys working except the highest pedal (this note has the contact broken off; I'll be replacing this...)
- seemingly all of the white toggle switches work, except that there's a bit of static in the "VOLUME SOFT" and the two echo switches
- flourescent light, "Rhythym II" unit, percussion section, and presets all work
- Serial #9445
- only 1 of 3 speakers is producing sound (Channel B according to the specs; if accessing the rear of the organ, it's the righthand 8")
- broken belt between tonewheel motor and the square scanner box (I added a rubber band for now & will order a new belt soon)
- every date stamp I've seen on parts begins with 67 (where #### seems to mean YYWW, according to other OrganForum posts)
- every tube emits a visible glow (no idea if this means they work, but they're all getting power...)
- a home-made 1/4" earphone jack was added from the 15" feed (it has no signal, just like the speaker itself)
- there's a slight hum from the Channel A 8" speaker that responds to the volume pedal; the hum is at the electrical pitch B
- the regular tone that's coming out of the organ now is pretty loud, but it's missing the low end and it's also missing out on brilliance (higher Hz?)
- the bench is covered with a worn out yellow/brown pattern padded cloth (hopefully there's polished wood underneath...)
- cosmetic condition is decent: the wood is nearly flawless; one E flat is damaged (cigarette ash meltage?); drawbar labels worn off; preset labels partially worn off
- it's freshly oiled as of yesterday (it came with a long skinny tube of hammond oil, which was really handy when oiling it...)

In short most of it works, with a few critical things to work on:
- getting the other 2 speakers/channels working
- freshening up the sound: possibly replacing/updating the electrolytic capacitors or ____ (?)
- seeing what's underneath that bench fabric

So, after the introduction, here are a couple of questions to the gang:
- given my description of the organ, does anyone know how to get Channel A and the Bass Channel working? (... the other two speakers)
- if parts need to be replaced to regain a full sound ("dried up electrolytic caps"?), where's the best place to start? I don't really care about "authentic key click" or other attack characteristics, but I do care about sustained pitches being as full-spectrum as they were back in '67.

Thanks!

[G4BVK]

Hi,

There is quite a lot of information on the H on the web. Having a good manual is a must.

My advice would be to start with the supplies. Check all of the HT, LT supplies from the PSU and not forgeting the -24 bias for the bass amp. Yes, you are right there will a number electrolytics that will need replacing. At this stage only replace the ones that are giving you a problem. You can go back go through the rest later. Most of my problems I found with my H were from the old carbon resistors. Power droppers and screen grid resistors are the favourites. Don’t automatically assume that the valve / tubes are at fault. Get them tested if you can, before you replace them.

Good luck.

Ken

[Waterloo]

Thanks Ken - much appreciated. What do HT and LT stand for?

[Waterloo]

Thanks Indianajo.

I removed the earphone jack completely and also tried unplugging/replugging the red and green speaker connectors. Neither had an effect, but I do like trying for easy answers first!

I tried wiggling the tubes as you suggested and there was a definite effect. One of the 6BQ5 tubes caused the Channel A 8" speaker to crackle (this is the speaker that otherwise only has a faint hum.) Nothing I did caused the 15" to crackle. Based on what you were saying, does this indicate a power supply problem or a problem in the connection to the preamp?

I've been looking through the service manual for weeks while figuring out which dusty box does what. I haven't soldered anything in over 20 years and haven't looked at a circuit drawing in 25. If cleaning and wiggling parts and ____ still result in only one speaker working, I'll start reading and figuring out how to replace parts without auto-electrocution :) Not a bad hobby for the summer/fall/winter.

I'll definitely do some before/after recordings once at that stage. Great idea.

[G4BVK]

Hi,

I suppose my back ground as an electronics engineer has trained me to look at problems in a particular way. Don’t change components on mass. The first thing is to find the fault or faults. Like I said, start with the main power supply unit (PSU), which is located in the bottom left side of the organ. Remember, there are high voltages in this unit so great care must be taken You should be able to check all the supplies from the multi-pin sockets with a mulimeter. The pins are numbered on the circuit.

I mentioned the -24v supply as well as providing the bias to the bass amplifier it also feeds a small PCB located just be hide the soft key. This unit is not in the main circuit diagrams. As far as I can see it designed to short circuit all audio feeds from organ if the -24v is lost. On my H100 I had a small cap on this PCB go bad, causing the loss of all audio feeds to the amplifiers. It took me several days to find this one.

You asked what were HT and LT. HT = (high tension, high volts) LT = (low tension, low volts). The HT will be around + 300 - 400v and the LT will be around 6.3v AC.

If you find that all of the supplies are good then move on to the main amplifier. Switch off the organ and remove the four screws holding the amplifier in place and you should be able to slide the unit forward; then tilting it backwards to expose the components. Have a good look at all the components; you are looking any resistors that are discoloured or any caps that are spit open. There are many things you can check when the power is off. You will need to understand the resistor colour code. You should be able to obtain this from the web. At this stage only replace the resistors that are more than 30% off value. Carbon resistor goes high in value over time. Try to follow the circuit as you go through the components. There are only three caps in the amp that may give a problem and that is C332, C350 and C366. They are all 20uf & 50v.

If at this stage you are still unable to find the fault it would mean powering up the amplifier, working on it HOT. I’m not too sure if to encourage you to expose yourself to the hazards of working on equipment with HIGH VOLTAGES, unless you have experience in working with high voltages.

Good luck

Ken

[Waterloo]

Thanks again Ken - this is really helpful. I'll look for the mystery unit behind the soft key next.

I found some color-code resources online and have found other online resources too (electrical basics, replacing old capacitors, etc.) Don't worry, I will be the most cautious debugger on the block when it comes to messing with electrical parts I don't yet understand.

I appreciate your approach of starting with the main power supply first, then going from there. My approach is different for now: try a few easy answers and hope the 3 speakers get going. I'll move to a more systematic approach shortly.

This project will be on the backburner for me for a week or two - I'll post updates here as anything interesting unfolds!

Thanks,
Curtis