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Messages - LBeast

Quote from: Tassieviking on December 01, 2023, 12:42:31 PMWould you be able to check the reverb tank for the model ?
I might build myself one of these and the reverb tank information is not on the schematic.
If you could provide all information you can see on the tank I should be able to work it out.
Hey Mick,

Be glad to. I'll pull her apart tomorrow and send you some pics/info. It is an Accutronics brand just like Fender uses. That much I know of off hand.
Quote from: Tassieviking on November 27, 2023, 08:06:25 AMThat is a very common relay so most mayor electronic companies have them.
Mouser, RS-Electronics, Element-14, Digikey, etc. just google G5V-1 relay.
If it was the relay not working then the LED's should still work.
I still think you are loosing power somewhere between the 58V (B)and the earth end of the 2k2 resistor.
If I am correct that the LED's are swapped on the schematic and terminal X has to be connected to earth for the overdrive to be on then the problem would be between the 58V and the grounding on the treble pot switch or the foot switch jack.

Are you using the treble pot or the foot switch to select the overdrive channel ?

If you are using the treble pot then try the foot switch instead and see what happens.
If you do not have a foot switch then insert a normal mono plug into the footswitch jack as this should work as well. (guitar lead will do)

Try the opposite of what you have been using to try to eliminate the fault.

It might be a bad part or component, but more likely a solder joint that has gone bad over time from vibrations.

Thanks for the relay info. Sounds like it may not be the problem, as you surmised.

I was using the amp with treble pot pulled out. I thought the same as you, that I could possibly use a foot switch instead to switch channels, so I tried that and there was no change in operation; still no LEDs/distortion channel.

I have been busy with other more serious life related things this week and may not get to firing up the soldering iron until this weekend. I also need to get a loupe or other type of magnifying equipment to try and track down any breaks in solder.

I really appreciate all you have done so far. You really know your stuff about electronics and schematics. That was a killer relay schematic you drew, I assume using some sort of CAD program. You really went above and beyond there. Looks like drawings my dad use to do when he was a designer using CAD. Sweet.
Quote from: Tassieviking on November 26, 2023, 12:24:51 PMThat 5W resistor must be original if both have it I guess.
I had a quick look at the PCB track picture I found on SSGuitar, I painted in the relay and resistor to see how it was set out.
I think the small relay might be similar to an Omron G5V-1 relay.

You cannot view this attachment.


Thanks! That is some jam up PCB detective work.

Any ideas on where I could purchase a new relay if it is the culprit in this situation?
So here is a picture of my working RG150ES head PCB board, also built in 1990. I have never opened this head before. I see the same powder on the same resistor. I did this to determine if the resistor in question in the RG50-112 was factory. From this picture it appears that it is, as both 50 watt PCBs are most likely identical.

BTW, this head sounds amazing with an overdrive pedal to push the front end. I play it through a Marshall 4x12 with English made greenbacks. Mmmmmm.........Butter!
Quote from: saturated on November 21, 2023, 09:50:54 PMHi LBeast
go to preview post and try to do it from there
(I didnt figure this out somebody else did possibly G1)

good luck with your amp and welcome to the forum

Much thanks to Saturated for helping me figure out the attachment process.
Here are some pics of my RG50-112 guts for errbody.
Quote from: Tassieviking on November 24, 2023, 01:53:47 AMIf I have the facts right, the following happens:
1.Distortion channel stops working but amplifier still works but only on the normal channel.
2. When this happens both the normal and distortion LED's go out.

When you want to use the distortion channel you have to pull the Treble knob out, or use the foot switch.
The relay operates and switches the amp to the distortion channel, the relay determines the channel that is used.
power is lost to both the LED's and the relay when fault appears, pointing to the 1k5 1w resistor to me.

I would suspect that the power to the relay goes out, possibly a bad solder joint or a faulty 1k5 1W resistor that goes to the relay from the +58v rail.

It is strange that you are worried about that power resistor that is also 1k5 that is dropping all that powder, there are only 2x 1k5 resistors on that schematic that I can see and they should be 1 watt.

In a previous post the same component was questioned.

I think you should try to trace where the 1k5 resistor is that feeds the relay, and then replace it. also re-flow all the solder joints in that part of the circuit.

If you take the PCB out and take some photos of the bottom tracks and the top of the PCB we might be able to help you trace it better.
Inspect the solder joints with a jewelers loupe or strong magnifying glass and you might see the problem.
I have 3 jewelers loupes I use for that job, 10x, 20x, 30x magnification I got from E-bay for dirt cheap. Best buy I ever did.

Edit: I think the red and green LED might be swapped around in the schematic as well.


That explanation is kind of it in a nutshell. I will pull the PCB out and look at the hidden top side of the board to see if there are any bad cold solder joints; crossing my fingers that re-soldering any possible bad solder joints does the trick. If not I'll try to go further to trace the bad component.

The sand resistor that dropped powder is a RGA 1.5k ohm 5% CW5 which stands on one end located toward the front of the amp near the master volume control. Again thanks for the help.
Hi G1,

Ah okay. Thank you for correcting me. I just couldn't find RL 1 on the SS schematic, because I was looking at the wrong schematic, though I did find it on the TC schematic. My fault. Showing my noobies. I'll take a look again at the proper RG50-112 schematic. Thanks for zeroing in on it for me above.
Hi Phil,

Thanks for the tips. I think you are referring to the RG50TC schematic, the RG50-112 that I have is SS and was built in 1990. It has a 1/4" jack for the footswitch instead of the old style 6 prong one my RG100ES has. Not sure what changed between the SS to the tube version.

Having difficulty uploading pics. I suppose I have to host the pics somewhere else and add the link in. I guess it is painfully obvious I haven't been on a forum in years. 😜 Hopefully you see the links I posted.
Thanks for responding and supplying those schematics. This is a SS version RG50-112. Since I am a novice, schematics are very much Greek to me. However, I can try to take a pic of the board tomorrow and highlight the cement resister which appeared to be shedding material; that way if you already know your way around the circuit, you can possibly pin point it on the schematic for me so I can possibly learn how to read schematics somewhat. I thank you both in advance for valued assistance.
I am new to the forum and am looking for some help regarding repairing my favorite Randall RG50-112 combo amp. Over the years the distortion channel has intermittently stopped working and then would return to working, if I left it alone, for a few days. However, now it seems the problem has become more acute, and the distortion channel is no longer working. Both the normal channel and the distorted channel lights LEDs do not work when the amp is acting up like this. I opened up the amp to see if I could see any solder joints which may have been broken, and I found a cement (sand?) resistor that appeared to be disintegrating as there was powder below it on the PCB board. It is near where the distortion channel knob for master volume is located and thought that may be the problem. I am not an amp tech, but I can replace a component here and there if I know what to replace and how to diagnose it. However, I am a complete amateur/novice at electrical repairs. Any help would be greatly appreciated.