Rheem/Califone 1909R - Need Help!

[dickard]

Hello all,

I just traded one of my guitars for a neat looking Rheem/Califone solid state guitar amplifier. It is in very rough shape, and I'm hoping it's not going to be a lot of work to get it working right again, but I'm not sure.

I'm curious if anyone has any experience with these amps. The circuitry looks pretty simple, but without a schematic I'm not sure that I can figure out exactly what's going on in there.

Any advice pointing me in the right direction will be greatly appreciated.

Rich

[52 Bill]

Welcome to the board.

What does the amp do or not do? Does it power up? Does it pass any signal?

[dickard]

The amplifier does power up. The speaker is not hooked up right now. I tested the amp out with headphones at low volume. There is lots of humming, and the sound coming from the guitar I plugged in was very distorted, and then I didn't get any sound. I think I might have blown the headphone speaker. I'm not sure about that. There is one axial capacitor that is only connected on one side, and a diode fell out of the bottom of the cabinet when I turned it upside-down.

[olddawg]

The amplifier does power up. The speaker is not hooked up right now. I tested the amp out with headphones at low volume. There is lots of humming, and the sound coming from the guitar I plugged in was very distorted, and then I didn't get any sound. I think I might have blown the headphone speaker. I'm not sure about that. There is one axial capacitor that is only connected on one side, and a diode fell out of the bottom of the cabinet when I turned it upside-down.

At first guess, off of the cuff, it sounds like you may have lost one of the diodes out of a bridge rectifier circuit in the main power supply and the associated main filter cap is disconnected. The diode may have simply unsoldered itself from years of heat and cold cycling, but more than likely someone has been troubleshooting the amp for a short. Before you turn it on again make sure it has the proper value fuses in it and meter out the output transistors. Get a schematic. Of course this is stabbing in the dark without seeing anything.

[52 Bill]

The fact that it powers up is a good sign. Before you do anything else, put a voltmeter across the output/speaker leads. Is there dc present? If there is, you may have killed your headphones.

Look at the board and see if you can see if someone's been there before, as Olddawg suggested. If the diode is part of the power supply, there should be at least one more just like it still on the board. See if you can find it, and find where the one that fell out came from.

Where does that cap fit in? Power supply? Power output stage? If it's from the power supply check it, and see where it belongs. Does replacing it reduce the hum?

Even without service information, you need to get the power supply working first, then the power amp, and then the pre-amps, etc.

Is it a plus and minus supply? If it is, there will be either 2 or 4 diodes and two large filter caps. Check them all and see if all of the correct voltages are present. In most commercial amp designs, the power supply filters caps will be rated at slightly more that the voltage from the power supply. So if the caps are rated at 50 volts, look for at least 40-45 volts.

[dickard]

All right! I'll check all those things out. I've got to get a new battery for my DMM before I can take any measurements. I'll let you know what I find out.

Thank you so much for your help and suggestions.

[wolf1419]

All right! I'll check all those things out. I've got to get a new battery for my DMM before I can take any measurements. I'll let you know what I find out.

Thank you so much for your help and suggestions.

This may not be very technically helpful, but this was a blast from the past for me. My very first electric guitar and amp were a Lafayette 3 pickup guitar & Rheem Califone combo amp(both brand new), from E.U.Wurlitzer, Boston, Ma.. As I remember I was very excited at first, but the thrill wore off very quickly because they had many features and were inexpensive, but didn't hold up to the tone of my friend's Fender gear. That was circa 1967......Good luck with your project....who knows, it might be a weird collectible or something with a unique sound...................jogged my memory....very cool!!

[dickard]

Well, I've got it working.

I removed the electronic section from the cabinet to get a better look at things. After checking out the circuit a little to try to figure out what was going on, I plugged it in, powered it up and checked a few things with my scope. The diodes in the power supply were in place, and the supply seemed to be working properly. I hooked up my signal generator and checked the signal at various stages thoughout the circuit, and all appeared to be functioning, with no DC present at the output. Knowing this I decided to hook up the speaker. It was working fine with the function generator, so I plugged in my guitar and played around for a bit.

I came across a couple issues:

- First, the tremelo isn't working.

It appears as though there is a lightbulb(!) missing from the circuit. I've never seen this before. Are lightbulbs usually used in tremelo circuits? I imagine that will be easy enough to source.

- Second, the reverb is very weak.

I tried reversing the cables from input and output. When I did this, I got a pile of feedback from the reverb pan even with the reverb potentiometer at a very low setting. I think there is something wrong with the reverb, but I'm not sure. Anybody have an idea? I really hope that I can get heavy reverb without the feedback somehow.

So far it sounds pretty nice. The pots could use a cleaning, and the cabinet could use a cleaning as well. I'll get to that eventually.

[JCHaywire]

Rheem Califone Amplifier

Just responding to this rather old post in search of a quick tip. The tremolo bulb/light-sensitive resistor--there is a component connected directly to the black wire of this light bulb. I my amp, I blew it up by placing my scope probes across those two terminals. I have only the charred leads remaining. All photos I have of the chassis show the two parallel 30MFD electrolytics obscuring this small white, tubular component. My amp is the 1907, but I suspect the topography of these models is very similar, especially how the tremolo is produced. I tried a diode in that position and a .1MFD NPO capacitor, neither of which allowed the bulb to light. If I had a photo or schematic or even someone's account of what that exploded component was, I could go from there. I know it was axial, and I know it was in glass or ceramic of some kind, but I don't know the value or even what component it was, really.
Any ideas?

Jonathan "JCHaywire"

Well, I've got it working.

I removed the electronic section from the cabinet to get a better look at things. After checking out the circuit a little to try to figure out what was going on, I plugged it in, powered it up and checked a few things with my scope. The diodes in the power supply were in place, and the supply seemed to be working properly. I hooked up my signal generator and checked the signal at various stages thoughout the circuit, and all appeared to be functioning, with no DC present at the output. Knowing this I decided to hook up the speaker. It was working fine with the function generator, so I plugged in my guitar and played around for a bit.

I came across a couple issues:

- First, the tremelo isn't working.

It appears as though there is a lightbulb(!) missing from the circuit. I've never seen this before. Are lightbulbs usually used in tremelo circuits? I imagine that will be easy enough to source.

- Second, the reverb is very weak.

I tried reversing the cables from input and output. When I did this, I got a pile of feedback from the reverb pan even with the reverb potentiometer at a very low setting. I think there is something wrong with the reverb, but I'm not sure. Anybody have an idea? I really hope that I can get heavy reverb without the feedback somehow.

So far it sounds pretty nice. The pots could use a cleaning, and the cabinet could use a cleaning as well. I'll get to that eventually.

[dmeek]

There are some photos of the 1907 on this page. It looks like a diode. Maybe like a 1N4004.

https://www.tdpri.com/threads/rheem-...ection.965229/

[g1]

I guess you put your scope ground in there?