Randall rg100 Es ?

[888guitars]

I called them(and emailed) as a former retail dealer and service center for Randall/ US music ( which is true ). Nothing yet.

[J M Fahey]

As a personal comment/pet peeve and related to this:
I am not Randall by any means , currently working alone and selling just a few amps a Month, NO time to answer phone calls personally and even less to shoot the breeze discussing gear, musicians, music or girl/band trouble with a customer for 1 or 2 hours non stop (somehow they always seem to have both the time and the stamina) so my phone greeting message says, literally:
"hi, you have reached Fahey Amps, can't answer now, please leave phone number, spell it *clearly* number by number, your full name as in the ID document, any nickname if I know you by it, what are you calling for or what is your problem, amp model, if mine state approximate date of purchase, I will call you, thanks"
Mind you, I am *offering* to call him back ... just ask for enough data to reach him and most important, to find him in my extensive customer database and know what are we talking about.

Typical answers?
"Hi Juan, I'm calling you from here, remember you made an amp for me? My friend wants another , he LOVED it , he has the cash, phone me when you have one ready, you already have my phone/look at the invoice/look at your caller ID screen/I'm the guy with the weird haircut/tatoo/piercing/leather jacket/who arrived in a motorcycle/who bought some pizza/helped you mount the speakers/went with 2 friends/etc."

Absolute worst is that 6 months or a year later they post in some crummy Argentine Guitar Forum and write: "I don't understand crazy Juan, I called him, told him I had the cash and he didn't even call me back"

Multiply this by 1000 and you reach the large Company message situation.
As Enzo said, you want to make it easy for them to answer you.
Worst case, politely ask again, with full data every time of course (NO "I left my full question 1 month ago, just check your records")

[J M Fahey]

Here is a RG80-RG100 schematic from the 1997 series and you can see the relay being used for channel switching by this point.

I can NOT understand this schematic.
relay shows connections to points called P2-1 , P2-3 , P2-4 , P2-5 , P2-7 which appear nowhere else in the schematic ... wtf?

and P2 (ribbon connector?), shows only 5 cables, while above reference reaches at least 7

[MarkusBass]

I can NOT understand this schematic.
relay shows connections to points called P2-1 , P2-3 , P2-4 , P2-5 , P2-7 which appear nowhere else in the schematic ... wtf?
and P2 (ribbon connector?), shows only 5 cables, while above reference reaches at least 7

This is easy: connector P2 (7 pins) on the amp board connects to connector P1 (7 pins) on the rear board. Connector P1 (5 pins) on the amp board connects to P2 (5 pins) connector on the rear board.
Juan, you assumed that they followed simple rule that net symbols with the same name are connected (like in Eagle, or KiCAD) but they didn't

Mark

[888guitars]

Oh I understand and really don't even expect a reply. I hope I didn't make it sound as though I was unhappy. I'm "in the business" as well, and I get it.

[teemuk]

I agree, terminal designations are quite cryptic at least. But you can make some sense out of it: PSU/PA board and the preamp board seem to use their own designations and at least some "pairs" are easy to locate.

Terminals P1/3 and P1/7 in the preamp board schematic must constitute the channel switching feature, since there is no other mechanism for it depicted. I suspect it's a simple "shunt-to-ground" -muting setup where one terminal is "shunted" while the other is left floating (and to pass signal), and vice versa when channel switches. Indicator LEDs are probably involved.

Do note, each board uses its own designations so don't expect to find connecting terminal "pairs" that carry same label. Perhaps that helps. I'm pretty sure that if you routinely follow the connections around P1/3, P1/7, the relay circuit, and the LED indicator circuit, you find a pattern and solve how it works.

I assume there is not "Sustain Boost" -feature in this amp, nor associated diode clippers, since the power amp stage includes the "Kicker" circuit, which equally serves as gain boost.

[J M Fahey]

This is easy: connector P2 (7 pins) on the amp board connects to connector P1 (7 pins) on the rear board. Connector P1 (5 pins) on the amp board connects to P2 (5 pins) connector on the rear board.
Juan, you assumed that they followed simple rule that net symbols with the same name are connected (like in Eagle, or KiCAD) but they didn't

Mark

Yes, foolishly I assumed a "Big Company DESIGNER" would

Oh I understand and really don't even expect a reply.

Don't worry
Just write/call now and then, someday a secretary will send your demand to some Tech Dept guy and he'll scan and send you a schematic.

That said, and given the nature of TL604: 2 SPST switches, interconnected so 1 opens and the other closes and viceversa, there's only 2 ways for them to be used:

a) one shorts channel A volume pot to ground when the other ungrounds Channel B volume pot , exactly what original switcher did and was replicated by relay switcher.
To me it looks like the "most probable" one simply because in concept "it's always the same" .
The only problem with this is, as they say, "the Devil is in the details" ... in this case this "relay substitute" looks functionally the same ... with the important difference contact resistance is NOT 0 ohms.

IF so, please measure TL604 trigger pin 2 voltage, tell us value when Red/Distortion channel is ON and when OFF .Then same voltage when OFF can be used to trigger an extra gate/FET which mutes Red channel at an earlier stage, while still muting its output; that should kill it for good.

Notice that this add-on does not even need us having the updated schematic to be applied.

EDIT
forgot:
b) there other way to use them: series switching (as opposed to grounding), each switch receives one channel output or simply sits in the signal path, when one is enabled the other is open, and viceversa.

In any case, we can apply our extra mute just reading the trigger signal, no need to know what the TL604 is actually doing.

EDIT 2
Notice that the schematic is *wrong* .
Found at least one extra error: IF Green Channel master volume, VR2 is set to 0, *both* channels are muted.
And if green channel is set to 10 and Red channel is selected, again both channels become muted.

Just guessing, and seeing this is a 1997/98 dated drawing, way after the "golden era", *maybe* this was just a copy, drawn by a not too skilled apprentice, poorly copied from some fading photocopy or moth/rat eaten blueprint.
Just guessing of course.

[MarkusBass]

I'm not sure what exactly is the problem with the amp. The original question was:

Does anyone know if you plug in the foot switch on the Randall RG100 Es , will it truly separate the channels?

and it was answered in the second post.
@888guitars: do you have the footswitch and tried it with the amp? We are focusing on the analog switch and incorrect schematic but if you have the footswitch, the problems are not that important. If you don't have the footswitch, you can easily buld it and make a quick test. Have you tried it?
Or, there is another problem with the amp?

Mark

[888guitars]

I just received my 6 prong plug to make my own foot switch. I looked at the schematic and it looked weird to me that both channels were "always on". I thought about trying to make a switch to ground the INPUT of each channel. I am not sure but I think it might be better as the guitar signal wouldn't get split in two? It's not like there is a buffer at the input.

[J M Fahey]

Switching the inputs will leave the channel going full blast even if "muted" and you'll have a mountain of hiss all the time.

From what we've seen this kind of Randalls mutes channels by grounding in turn the corresponding second volume pot (may be labelled volume or master) which is as late as you can go before mixing them.

I still don't know how can the TL604 leave both channels on , with or without footswitch , because it has 2 *linked* switches, while one is ON, the other is OFF and viceversa.
They are never both ON or both OFF and they are NOT independent.

[888guitars]

I have wired the foot switch and channels do switch but only my red led on both the amp and switch come on? Both green led's test good. Something is weird here?

[J M Fahey]

Measure voltage each side of suspect Leds and activate footswitch buttons in all combinations, even a good Led won't turn on if same voltage on both pins.

[888guitars]

Because I got in the Randall thing. I picked up a rg100 classic. This was obviously made later with on board channel switching and the "kicker" boost from a footswitch.( which sounds to be just a volume boost) I will open the thing up tonight and see if I can find a date in it.
Anyway, it sounds GREAT! Maybe the "ES" or extra sustain was just now built in the circuit as it has a lot of gain! I'm lovin' it! ( Mc Donald's tag line

[loudthud]

Does Peavey still sell the little circuit they used to replace TL604s ? It was a little circuit board that was connected to the main PCB where the TL604 was removed.

Edit: A couple of threads on the subject:
http://music-electronics-forum.com/t10372/
http://music-electronics-forum.com/t2196/


I thought there was one with a picture, but can't find it now.

[888guitars]

That's news to me? My shop is still a peavey service center, I might call them tomorrow