Flying Blind with Rita- A Wurlitzer 300 Story

[bachelorb]

I am going to need some help if yall don't mind. I have never repaired an organ before.

A little bit of a backstory, I am a cowboy chord guitar player, who loves old American made instruments. I ran across this old 300 and couldn't resist. It was all working along fine for what I do….. which is add a bit of "color" to my guitar recordings. I went to fire it up last year, and the lower manual, lower switches and pedals had quit working. Upper Manual and volume pedal work fine.

I have worked on electronics and gotten a few soundboards working with my redneck signal generator and a multimeter.... I also know all about being zapped by power supply caps 😀

So far, I've checked the fuses and they are fine. I was going to Deoxit all the connectors except...... except....... there aren't any 😲.....and now I'm stuck..... I can't find any block diagrams, schematics..... anything. It looks to me like pedals, switches, and lower manual all hook into the one lower board at various places.

This is a Wurlitzer Model 300 Digital Music System I've named Rita since there was a plaque on it in her memory. Any previous model information on similar organs or on this one would be greatly appreciated. I know its not worth a whole lot, but it's what I got...... Thank you

Brad Bachelor

[bachelorb]

Yesterday was research day, and there was not a whole lotta luck. Even Jan’s huge list of organs doesn’t have my model on it. …..

I am going to try to do a couple of things today.
1- Trace power- It seems odd that both the pedals and lower manual are down. My first hope (improbable) is for a loose wire.
2- Trace signal- first I have to modify my signal generator with alligator clips, but then I can trace signal from the pedals to the lower main board and the lower manual to the lower main board…. after that, I think I’m through without a schematic.

I am going to see if Morelocks has a service manual on Monday. Does anyone have Morelocks email address that they could pass along to me?

[you795a]

You can check for voltages on the board and also the wire wrap connections. It looks like those ICs and LSI and are CMOS and therefore static sensitive. Be careful you don't zap them with static. At this point I don't know where you would go for parts and/or information as the place that had them is no longer in business the way it seems.

[tucsondave]

The common connection between pedals and lower manual on organs is the rhythm section. If your organ has the ability to pulse the lower and pedals then clean any related switches.
I don't have a service manual for the 300 but Wurlitzer used "Touch Tone" and "Dancing Chord" on some models that would affect the pedals and lower manual.
Morelocks has closed.

td

[bachelorb]

Thank you guys….. I have injected a signal into all the boards based on the same wire color on each board. The percussion and, upper board came up to 15mV at the amp. The lower board was less than 1mV at the amp.
tucsondave I have both the “touch tone” and “Dancing Chord” on mine. I wonder if I can isolate that somehow?

Morelocks has closed.

ugh…… this thing gets closer to the dumpster everyday…..

[tucsondave]

Are the slide pots broken or missing or is it just the photo lighting?
I see what appears to be liquid stains on some of the boards. Is there any corrosion or signs of a rodent having been in the organ?

td

[tucsondave]

Looks like a D-4.
Does this match your left hand cheek block PC board? Panel layout? Are chips on the lower keyboard # 149776 or 74LS151?

[bachelorb]

Thanks Dave for taking your time on this.

Are the slide pots broken or missing or is it just the photo lighting?
I see what appears to be liquid stains on some of the boards. Is there any corrosion or signs of a rodent having been in the organ?

td

There are liquid stains, but it’s been in a climate controlled building since I’ve had it working. I couldn’t see any signs of rodents or rodent damage.

The lower keyboard chips are 74LS151‘s. The slider switches are missing their plastic tops is all. I’ve hit them with some fader lube. The board layout is close. Pins don’t quite match up physically in their position.

That switch layout is just like mine except mine doesn’t have the programmable registration, so I’m leaning to the D-4

[tucsondave]

I posted the wrong pc board pic. PM me an email address and I'll scan the D4 pages. The service manual is D4, D5, D15, and D16.

td

[tucsondave]

Now that we have determined that it is a D4 I'm curious about the model 300 plate.
Perhaps andyg would have some insight.
andyg?
andyg?
Bueller?
Bueller?

[bachelorb]

Well….. an update….. I didn’t find a thing today…. All the voltages are in spec, and somewhere in the board, I lose signal.

Question: I’m worried those LSI’s were programmed… were they?

Tomorrow, I’m going to print off the schematic and start marking off the signal lines as I check em……

[bachelorb]

@Tuscondave helped me above and beyond, but the apprentice who had hands and eyes on this thing (.....me....) is dumber than a sack of hammers when it comes to logic circuits. I've looked around for an old d4/d5 parts organ, but there is nothing near me, sooooo I think I'm going to give up on this one...... or am I???

I've got an idea to take my Korg Monologue and put it where the lower manual of this organ is. I would need to fashion some type of "line in" to the current organ amp for the Korg. Is this possible? The current signal lines at the amp are powered at +9 ,-12, and -24 DCV.... Line inputs are in the mV.....

I'm just thinking out loud, but since the upper manual and voicing still work, it would kind of be nice to having the synth right below it..... and I could use the headphone jack as a line out....... any thoughts??