Always. 2 transistor get hot, 2 remain cold all the time.

This pic shows the transistors. Two of them work, I mean they are hot when working, the other two are inactive and totally cold.

The resistor is missing.

It seems the amp lacks power, it sounds ok but seems to have a low output.

Help?

It would be of great help the schematics of the amp: Randall Century 200 II. Impossible to find, even at Randall

Hi, I'm a proud owner of a Randall collection. My Century 200 II seems to have some problems. There's some missing component in the PCB. The amp lacks power and two of the four power transistors are cold when working (they are NOT working).

Her's a pic of the whole circuit, and a pic of the missing (seem to be cut) component. My electronic repairman says is should be some kind of resistance. Some help? I need to fix this a.s.a.p...

Thank you so much!  :tu:

Well, in fact I don't want the "Both Channels" option active... so I guess I could make a 1 jack cable just for switching channels... am I right?

How can I make this?

Roi.

Hello again!

My question this time is about the Randall RG100ES / HT footswitch.

I need to control the channel switch of this head (it uses the 6-pin connector) with my Behringer FCB1010 floor controller (wich uses standard mono jacks for switching). Is this possible?

I mean, I need to make a cable that goes from the 6-pin > to two 6.3 jacks. Is this possible, and how do I make this cable? I have the original Randall fotswitch schematics but I don't understand it.

I have a Randall FS5 footswitch so I can use this 6-pin connector (which seems impossible to find here in Europe).

Thank you very much.

Roi.

Hey! Another couple of questions for the experts, help needed!

1/ Well, my RG100 Classic haas really high gain, no need to use a Booster. But with ALL other amps I'm using a booster before the amp (and a Parametric EQ) to have infinite gain and that chainsaw metal tone. Is there any difference in them in this point, I mean, input gain?

2/ My RG100HT (blue rack unit) has an extreme hum noise problem, which I've seen is a common problem in this model if using high-gain settings. Is there any way to solve this? At his moment, and usin gain at 10 as I do, it is really hard to play it.

Thanks..

Thank you very much again for your help!

Hi!

Well, I've contated an electronic engineer who finally will do the job.

One more question:

Quote) "Tame" your Randall by soldering a 15K resistor from the left pin of R45 to the right one of R46.
Left and right as seen on the schematic, on the actual board they might point anywhere.

Why? What's this about? And what do you mean by "tame"?

Thanx again.

I've just seen in the RG100ES manual (page 4, "back panel") here:

http://www.schematicheaven.com/newamps/randall_rg100es-rg80es.pdf

that the "direct out" is a "preamp output", not an attenuated speaker output, isn't it?

So if I unhook the power amp section, this direct output would be still active. (And I would still have to attenuate this signal 10 db or so to feed the "line in" in my FX unit).

Roi.

Hi again, and thanks for your fast reply.

QuoteIf it clips your powered mixer, probably the direct out pot isn't working properly.

It's not a powered mixer, it's a Soundcraft mixer with +30 dBu headroom line in, and as I said ALL heads clip ery seriously that line in. I doubt 4 heads having the direct out not working... The only one that has a specific direct out pot is the RG100HT. The others (RG100ES, RG100 Classic, and Century 200 have the direct out level controlled by each channel master pot.

All of them clip. One electronic engineer told me today that I need at least a 10 dB atttenuation to feed a conventional +4 dBu line in. Would it be OK?

QuoteOnly way you can operate them as preamps, is to unhook the PSU for poweramp, so the only thing working in the circuit is the preamp, and you hook it to mesa or whatever via effect send jack.

That's what this friend of mine recommended, but I wanted to have a Parametric EQ and a compressor in the loop, and then use the direct out. Do you mean the direct out is located in the power amp section? So would it be the same to use the FX send out? I've read that some guitarists (e.g. Darrell, Lynch) used to overload the instrument input AND the FX return to obtain more gain and sustain.

Thank you very much.

Roi.

Hi!  

I'm new to this forum so hello to all members. I'm coming here for some help.

I own a RG100ES head, one RG100HT rackmount unit, one RG100 Classic head and one Century 200 Head.

My questions are:

1/ Can I use these heads without my cabs? Any problems if working on max volume with no load?

2/ (The important question): ALL these heads have a "direct out" jack which I want to use to feed a Mesa Boogie 2:90 power amp. The problem is this direct out (+4 dBm) is clipping my processors, it seems to be a really hot line out. It happens in all the heads.

-Master volume pot in the heads goes from silence (in zero position) to total clipping (in 2 position), instantly, I can see it in the processors input LEDs. The processor can handle up to +4 dBu.

-I've tried this +4 dbm direct out into a mixer (its line out can handle up to +30dBu) and it overloads the input too.

-Could this extreme clipping be related to the lack of power amp load in some way? I can't understand what's happening!

I want to use two RG100Heads as preamps, being able to use their FX loops independently, then direct outs to processors, then to stereo power amp.

Thank you very much.