Welp- It was working good there for a while. Fired it up today and there was a lot of static and hum. Sounded OK for a few minutes but then went bad again but the hum was there much louder than I remember it ever being.

I'm assuming given the previous advice that new filter caps are in order.

I did run the preamp through another amp's power-in jack and there is no static. But there is still a fair amount of hum.

I opened it up and checked the resoldered joint but it didn't seem to be the problem. Nothing stopped the static once it started. No cutting in and out. Just once it starts it doesn't go away.

Any advice on what kind of caps to get and/or if I should replace anything else while I'm at it?

Thanks.

Chewy.

Update:

I changed the tubes and it really kicks but now!  :dbtu:

I got some Mullard EL84s new production and put those in first. My first impression was that they were thinner, quieter sounding and break up sooner than the stock tubes. I like the smooth breakup of the Mullards but I also like the full, low-end and clarity of the stock tubes.

I left the Mullards in though and tried swapping the Peavey Super 7 AX7s out for some tubes I already had on hand. After several combinations I found that a NOS JAN Philips 5751 in position 1 really added body, depth and put back that low-end the Mullards seemed to pull out. It also gives the clean channel a bit more headroom. Tried several other tubes including a NOS DW7 and AU7 (which both sounded more clean but had less "presence" I guess- quieter) and an Electro Harmonics AY7 which sounded great- clean and clear and sparkly. It also added depth like the NOS 5751 (though not quite as much) and also added a little more clean headroom than the 5751.

Then I put a Sovetek AX7LPS in position 3 which someone who tweaks Peavey's said this particular tube works well in the phase inverter slot. It did, nice clarity and fullness. I just happened to have this tube that came stock in an old Tube Works pedal.

Then I put a JJ 5751 in position 2 and didn't notice much if any difference from the stock Super 7. It sounded a little dark and muffled by comparison actually. But I put the Electro Harmonics AY7 in position 2 and it sounds MUCH better. The distortion is not as fizzy and it sounds full, strong and crunchy but the amp can still go REALLY over-driven if dialed that way. I can now get more of an old Plexi crunch in addition to all the overdrive I might ever want. If I had another NOS JAN Philips 5751, I bet it would work well in slot 2 also.

Leaving the Mullard EL84s in there for now since the low end seems to be back.

Gotta say I'm really thrilled with this little amp.  <3)

Thanks Enzo!

Ok- got 'er all cleaned up and speaker swapped. She sounds great and looks great! <3)

I did what you said Enzo for the effects loop jack and it seemed to fix it. Volume stays at the same level with the loop bridged or not. Thanks for that tip!

I left the tubes as is for now since it sounds fine to me. Might try swapping a few things out after I've played with it a while. I did pull the power tubes and "Made In USSR" is printed VERY lightly- almost missed it- but there is no brand name. Research suggests they might be Soveteks. Also heard Peavey may have used rebranded JJ or Sovetek 12AX7s for their "Super 7" tube. If the EL84s are Russian I suppose the rebranded AX7s could be as well. If these were made before 90 when the amp was built, I doubt they would be Chinese but who knows. At any rate, I'm very pleased with it.

The WGS Reaper helps a lot too. Makes it sound "bigger" and a little less harsh and mid-heavy than the stock Eminence.

All I got to say now about this amp is- "BRAVO!"  :dbtu:

Thanks Enzo- Got it all apart now. Cleaning and scrubbing! Cleaning and scrubbing!  :tu:

Cobwebs, spider eggs, pennies and original Peavey Super 7 preamp tubes! Power tubes are unmarked but it doesn't look like it has every been opened. Sounds really good though. Wonder if new tubes would make much difference. It's dated 1990- the speaker is anyway.

Everything is cleaning up well but the reverb tank. It has several quarter-sized corrosion spots on the top. Works OK just really ugly.

Got one of these today really cheap. It's dirty as heck and looks like it's been sitting in someone's garage for the last 20 years but it fires up and sounds incredible! When I first started playing though, the volume slowly dropped down to a very low level even with everything maxed. It sounds fine for the first few minutes then it just kind of slowly and gradually drops off. I read online somewhere a suggestion to bridge the effects loop with a patch cable and THAT WAS IT! :tu: Jammed on it for about an hour and never did get it up over 5 because it is now SO loud!  :dbtu:

Do I have to keep the loop bridged or should a good cleaning take care of it?

I plan to crack it open tonight and check/clean it out and at least replace the stock speaker with a WGS Reaper 30 I have handy.

Does anyone have any experience with this amp? Thoughts? Suggestions?

Chews

Happy to do it. Just wish I had a larger scanner. The documents were like road-map size!

Second post due to file limit restrictions. These are Service and Schematics documents.

I just got a Lab Series L6 bass amp in very good condition for a great price. The kicker is that the original service documents were in the original envelope glued to the cabinet! Documents include Description/Service instructions, schematics, circuit board diagrams and parts listings. I know these amps are rare but somebody may find these useful.

Also-

If you get the service warranty, check the rules because I was told they wouldn't do repairs until 60 days after purchase. They would do a full "no-questions-asked" refund during the first 30 days. Which leaves the potential for one month with a non-working amp that you can't do anything with. Then there is time in the shop which may be several months more and that is IF they can fix it. Again, I'm not positive on all this but seems like something weird like that. Perhaps someone else can clarify.

I generally just buy the stuff with no warranty. I accept that if something craps out after the return deadline, 1) I didn't spend that much on it in the first place. 2) I'm prepared to pay up to a certain amount to get it fixed locally by a reputable shop. 3) I may even be able to fix it myself and 4) unless it is an extremely rare item that I can't live without, I throw it away and go shopping again.

This usually makes the most sense with low-price items like this. If it was a $1,000 amp, I'd be more inclined to go with a warranty.

I would rather have the Randall than the MG also so it is not a bad switch IMHO. :dbtu:

I imagine it could be done with some sort of circuitry between one speaker and the other to delay the signal but I wouldn't know what that would be. Might be easy, might not. If you do it, I'd rig it so you can bypass it with a switch. I doubt you want permanent delay/echo effect on your amp. But whatever turns you on is what matters. :dbtu:

Here is your amp:

http://www.guitarcenter.com/In-Store-Used-USED-RANDALL-RX75RG2-108004547-i2648263.gc

Guitar Center will ship it to your house. Don't need a Guitar Center anywhere near you- just UPS service. Just order it via the web site or call the store and they'll ship it out. Doesn't matter where the store is either. I've bought several used amps from GC this way and been very satisfied.

It's used but you *can* get a service warranty but you'd have to ship it back or take it to your nearest GC for attention. If you don't get the warranty and you find something is wrong with it within a few days, they will take it back no problem with full refund (at least that's been my experience). Just call the store you bought it from.

Shipping charges are very reasonable from Guitar Center also.

Chewy

Not a theory, just a speculation...

Whatever is the specific cause of the noise from the reverb, it is directly related to the proximity of the tank to the speakers.

Just when I was worried I wouldn't have some new problem to fix... :dbtu:

I recently put a new set of WGS speakers in my Lab Series L5 and the magnets are so strong, they are distorting my reverb!

If I have the reverb up anywhere over 2, I get a harsh, clinky, metallic echo/delay effect then it goes to normal reverb sound. I assume this is the spring vibrating temporarily against the tank because the magnet has pulled it out of center and so close that it is vibrating against it at higher settings. I pulled the tank out while still connected and it works fine. I put it back in and shifted it over and away from the speaker magnets as much as I could and it is better but still there over 2.

Is there a material that can be used to easily, cheaply and effectively shield the tank from the speaker's magnetic field? Or is there something else I could do short of building a separate reverb tank unit?

Thanks.

For what it's worth, I had an "intermittent" failure going on with my Randall head that is the same age as your Peavey. It would drop volume and go fuzzy sounding. Sometimes come back to normal, sometimes not until after switch-off. Almost always failed after a bit of playing at above a certain level of volume.

Roly and DrGonz helped me diagnose and it turned out to be a bad solder connection on one of the filter caps. I cut fresh leads and resoldered and so far (fingers crossed) it hasn't failed again and sounds great.

Just took a lot of poking around and testing.