Peavey 5150 Combo in for a checkup. Anybody familiar with these??(New Info)

[Platefire]

This amp has to be heavier than a twin. I had help when I loaded it in my car but when I got home, I thought I was going to die getting it in the house. This amp is for folks who can afford Roadies!

The customer is not the player. It came from a church where it's been sitting up a while. When I ask him what the problem was he imitated a repeating oscillation noise.  

This is what I did and what I found. Both channels work. In fact everything works and there is no failure of any of the functions that I can tell. There was no footswitch with it but channel switching, bright switch, crunch switch and all knobs seem to be doing what they are suppose to. Even though this is a early 90's amp, it is in great shape like new condition and has not been abused.

I tried hard to make the clean channel sound like a fender but I couldn't even get close hardly--kinda sorta--but it was hard to get a good clean sound even with the MV 100% and using the pre-gain as vol. with the mid control up at all made it sound real nasal sounding. Wasn't really happy with what I was getting out of the tone stack even though is has T/M/B controls plus Resonance and Presence.

The drive channel was pretty good IMHO. The controls reminded me of my old Fender Hot Rod Deluxe I use to have but the drive channel sounds a whole lot better. It shines better than the clean channel.

The main problem I found with the amp is an overall "hissss" in both channels. In both channels if you turn the MV on 10 and put the pre-gain vol on 1, the hisss is pretty loud. If you play at lower volumes, the hisss is not as present but still audible. I tried an new 12AX7 in all the pre positions plus another 6L6 in the both positions and it had no effect on the hisss.

I've had no experiance with 5150 before so I don't know what I'm suppose to be getting tone-wise. This is a 90's amp, so may be due for filter caps but I don't know if that's what causing the hissing. Any suggestions on where to go first?? The only amp I ever had that had a hissing problem like this was my Silvertone 1482 and corrected it by replacing V1 cathode resistor. Platefire

[Platefire]

Regarding the hisss problem. I have since done some research on this amp and have found that the hisss is a common problem with this amp. You can do a google search on "Peavey 5150 white noise Problem" and find post after post on different forums of the same problem. Found a lot of Recomendations on all these post to use a noise gate in the effects loop. Some say use lower gain preamp tubes will help. I was able to get a better clean tone than I stated in previous post. Plugging into the low gain input helped, but took a lot of tweaking vol/tone controls to get there--but the white noise was ever present in the background---more than your normal amp. It was stated time after time on all the post I looked at, "This is a high gain amp, that's the way Eddie wanted it and is a by product of all that gain in this amp. So having read all that, I don't know if I want to even attempt to take on the white noise problem in this amp??? Based on what the customer told me, it don't sound like the original problem he referred too. I'll not do anymore until I discuss this with customer. Platefire
 

[PRR]

A 5150 in a church just seems wrong.

Work with one of your heavy-metal bar-band clients and do a swap for something less over-the-top.

[Willabe]

A 5150 in a church just seems wrong.

Work with one of your heavy-metal bar-band clients and do a swap for something less over-the-top.

Agree.


 

[Platefire]

  Jesus on the Main Line, Tell him what you Want!

[Willabe]

 

[Jack1962]

I have worked on a few of these , all of them hiss , it's a high gain amp man most of them have tons of gain and midrange . using lower gain preamp tubes help but I have never been able to remove all of the hiss from these or for that matter any of the high gain Peavey amps . I have however had a couple come in with oscillation problems and the problem in one was a bad preamp tube the other was bad solder joints if a remember correctly. I have to agree this amp would be a poor choice for a church amp unless it's Metal Church lol

[Platefire]

Don't know the status of the church this came out of. The guy that brought it to me my former boss before I retired that is an Architect and also a musician who assist in Praise and Worship in his church and is a conservative in practice and dress and to the best of my knowledge is not into metal. Seems to be a lot interest here why a metal amp came out of a church. At this point I don't know but may find out more as I confer with customer.

One thing I will say, I don't believe this amp has been used in a long time judging from the dust on it. If it had been used, even the dust around the control knobs would have been somewhat disturbed but I don't see it. From my conversation with my X-boss, I don't think he has any idea it's a metal amp.

If someone discovered this amp in a back room, tried to turn it on and it was set to a loud high gain setting and started squealing--they might have thought something is surely bad wrong with this amp

Anyway, it's like new like it's never has been used. Platefire 

[alerich]

I have owned a 5150 and a 6505 head. Heavy mothers. I once tried to pick up a 5150 combo. I gave up. I was convinced that someone had bolted it to the floor. I cannot think of a more inappropriate amp for a church setting unless the Reverend Rob Halford is presiding. Hissy? Yes. But nobody plays those with the masters dimed.

[John]

I'm betting the amp was donated to the church, and never used.

[6G6]

I think John nailed it. 

It is the nature of those, and most high gain amps to take just
a little hiss/noise and make it a lot of noise.

Maybe some young (and stong) metal head out there would gladly trade a good Deluxe Reverb for it.

[PRR]

I too think this 5150 became burdensome or otherwise un-wanted and "somehow" got into the church collection, never left, never played again.

A real foot-stomping worship might use a bass amp with that much brute POWER.

But unless the service is exclusively ROCK N ROLL, I can't see this kind of hi-gain (hissy-fit) sound fitting with preaching and choir singing. It's the elephant in the room, and it has gas. A worship amp should be subserviant to the service. IMHO.

Look at the schematic. SIX gain stages cascaded on the first page, and two more before the finals. Two gain-stages is often ample.

If this were the only amp in town, *probably* it could be tamed to something you could contemplate God with. But it's also PCB with a VERY messy heap of interconnectes to untangle. And it IS valuable as-is in a different venue (the Gin-&-Sin down the street).

I am reminded of a mildly offensive "joke":

Jewish Dilemma - Free Ham!
Jewish Solution - Sell the ham!

God may move in mysterious ways. In this case I think He gave this church "ham" which they may trade for the object they really want.

There's a bazillion good sturdy amplifiers which would be (IMHO) more suitable worship-mates than a 5150, for most worships.

> an Architect ... conservative in practice and dress and to the best of my knowledge is not into metal

It _would_ be good to go see their service. Sometimes you just can't tell about a person's worship just seeing him in the office. Maybe you walk in, everybody is wearing leather chaps (and nothing else), communion is lines of coke across the altar, and everybody worships the Guitar God. I don't say that's a wrong way to worship; not my job to judge. I do admit that for THAT sort of service, a 5150 may be essential. So spray the pots, re-cap, and chase bad PCB joints.

But IMHO 99% of services, even the foot-stomping style, would be better served by a Peavey Plain or Yamaha Simple Box, probably solid-state. Something a bar-guitar player might have from his starter days, or a rock shop would gladly trade for a 5150.

[Jack1962]

You do know that there are 3 version of the 5150 right

[Platefire]

Well since this amp came in I been researching a bit and found Fender now makes one, EVH has his own version and of course Peavey now calls it the 6150 or something like that.

The one I got is a 2-6L6 one but I think they made a 4-6L6 one or maybe a 4-EL34 one?? Heads and Combos. I've read where some metal heads swear by them. Regardless nobody should try to move one without help--you could do bodily harm to yourself trying to move it by yourself. Platefire

[PRR]

Yes, there's an original and several reissues, clones, copycats, and sounds-alikes. Peavey worked with Van Halen, then Eddie split. I think Eddie holds the rights to the name "5150". The post-Peavey 5150s have an "EVH" badge but appear to be built by Fender. The brands, model-numbers, and knobs change but the guts are all very similar. Peavey seems to be making six different "6505" models, with two or four 6L6 or EL34. EVH III has *eight* 12AX7, enough to make a flea-fart drown out Gabriel's horn.

All of them are brutal machines.

[yeti]

customer reports oscillation noise.

i would test/check the preamp and power amp tubes first.

filter caps next, though i suspect they're probably good.

screen grid resistors in the power section. if one is blown or bad you will get weird hum and odd noise.  if replacing one of them, now is a good time to increase the value to a more industry standard of 1k5w, or at least 480ohm 5w.  i would recommend this fix regardless, as these 100ohm stock Screen grid resistors are known to fail commonly.

beyond that, you'll have to try to replicate that noise and explain it better here.  have you tried running the amp loud, as in gig volume loud?  like 2 and higher on the post gains?  now see if it oscillates.


as far as the hiss, there are a few remedies i would recommend for this:

-drop the input grid resistor R16 on v1a (the first gain stage) down to 15k. or even 10k.

-increase v2a Rk (cathode resistor) R42 from 39k to 50k, or even 54k.

-on v5b, install a 10pf or 15pf silver mica capacitor from pin 6 to pin 7. this will smooth out the gain a bit and further reduced the hiss of this amp.

-you can also install a 1kv or higher bypass cap (value from 47pf -300pf) on v5b plate resistor R12 (220k).

decreasing the input grid resistor r16 value and increasing r42 value are the two easiest fixes, and you should see significant hiss reduction with both of those mods. 

[Platefire]

Yeti-Thanks! The customer tried to explain or demonstrate with his mouth an oscillation like noise that I never found. I have recently fired up the amp to conclude and verify my original findings turning up the volume a bit to the dismay of my ears(glad it's not the 100 watt version) to check for any high volume issues in which it performed fine. I do like the distortion channel because I could hear that classic marshall stack like bottom end thump there that I have been a fan of but not at close range. I can see where this could be a good tool for shreaders with all the high gain harmonics, squeals, squalks and feedback you can obtain with all your noodling and power cords.

The customer wanted what would be considered an non-normal amp problem corrected in which I can't find any. If it was a full fledged metal head communicating with me really into his game and could be specific about his issues with the amp--I would take on those issues and if it morphs into that I will then take it on and consider your suggestions. As of right now I'm done. Platefire
 

[Platefire]

Well this thing has morphed into something else. Everything we guessed about this amp previously was all wrong. Got a call from the player Saturday. This is the situation---The amp has been used on a regular basis on Sunday and Wednesday Church services. He said he only uses the clean channel and uses his pedals for effects. All was well for a long time on the amp and all of sudden recently blew the main fuse. They replaced the fuse and fired it up and began to play. The player noticed that the volume dropped and said it smelled liked something was burning. At this point he turned it off quickly.

I will reiterate I have played this amp several times without any problem and left it on for an hour the other day with no problem. Tested all operations--channel switch both clean & drive, reverb, bright switch, Crunch switch and all seemed to be performing well. I've tested in a low and high volumes. I have observed the tubes for red plating, no red plating. I didn't get the footswitch with the amp so all the functions were tested with the buttons on the control panel.

After I got the call Saturday, I pulled the chassis. It has four internal fuses beside the external main fuse. Did a continuity check through each fuse and they all had continuity. I examined the circuit board, wiring, connectors for any charring, burn marks or over heating discoloration and didn't find any signs. Understand that this is a Peavey with three boards boxed together in a U shape and not all the components are visable. You can't even see or access the board the tubes are mounted to. Anybody got any ideas? I'm not big on starting to pull boards for a better view but obviously something happened but I'm not getting any said symptoms from the live amp and not finding any damage?? Platefire    

[PRR]

Fuse-blowing has to be a HIGH power stage. Power supply. Maybe the output tubes.

Use a Bias-Rite to check 6L6 idle currents. Not for sweetness, just see if it's way-wrong (like 1mA or 100mA).

Jiggle a 6L6 enough to *carefully* probe pin 4, Screen. There's a big screen-feed resistor, it could be smoked, and you (not knowing what the amp should be) could be playing in bad triode mode and not know there's a ton of tone missing.

[Platefire]

PRR

I did as you said. The Ruby BiasMaster showed 4.5 mA on one tube and 21.3 mA on the other. The plate voltage is 509 on both tubes. The bias voltage is -53.4. Can't get access to C55 terms so I measured screen voltage form R103(220K) at 508V.

On the screens, I'm a little confused. Referring to the schematic on the top diode network/main high voltage power supply show screen voltage coming off C55 to screens that shows 475VDC . On the other/lower diode network it shows it shows another screen coming off R113(I think you were referring to) 2.2M. This can't be a screen resistor because it looks like a 1/4 to 1/2 watt resistor? I measured voltage on R113 and it has  500VDC on one end and "0" on the other end. Apparently this is tied in with the screen voltage an this(whatever it is?) circuit/diodes is labeled "Status" and "Power"?? 

Voltages seem to be running about 30V above schematic. Something is amiss with the 4.5mA. I popped in
a set of used(unbalance but working) Sovtek 6L6GC's and the bias read 29mA on one and 43.1 mA(mo better) on the other. Plate voltage dropped to about 500, screen 498 and bias-52.9. Just knowing that my own used set of Sovtek 6L6GC's were pretty unbalanced, it appears a new set of balanced tubes might do much.

As a side note--I tested the diodes in the power supply. My wally world meter test shows all the diodes as good with the little single short "beep" with +hot on the input, ground on the -output. With my Fluke 115 on CR 21, 26 and 20 I get a continuous beep which is suppose to mean they are bad? Not sure what to make of this? Platefire

[sluckey]

As a side note--I tested the diodes in the power supply. My wally world meter test shows all the diodes as good with the little single short "beep" with +hot on the input, ground on the -output. With my Fluke 115 on CR 21, 26 and 20 I get a continuous beep which is suppose to mean they are bad? Not sure what to make of this? Platefire

You cannot reliably check diodes in circuit. Unsolder at least one end.

[Platefire]

Sluckey

I checked the circuit voltages this power supply is feeding and they seemed to be good. So rather than pulling that board and do that, I will assume they are working OK for now. Thanks, Platefire

[sluckey]

That's a safe assumption.

[PRR]

> Something is amiss with the 4.5mA.

Eh. If it were used *as intended*, nobody would notice a lop-sided idle (headbangers never play soft).

OTOH while 4mA-20mA isn't "wrong" for such a cold-bias amp, it does make us wonder if one or the other tube may be sick.

Since it seems to be used in a non-crazy venue, you might sell them a better matched pair of tubes just as general good practice.

Hate to say it, but if you can't beat it into a failure at your shop, you just might have to go to an evening choir practice so the player can show you the problem.

[Platefire]

Har! If it wasn't for the weight I would already took it to my Church, set it up and used it a while. After unloading this by myself when I got home, I felt it in my back that night. So I'm not wanting to move this thing any more than necessary. I got a little dolly I might try? Platefire 

[hesamadman]

The only practice use I have ever seen for these amps, are in any band tuning to a drop Tuning. Mainly lower than D. All the way to a#. While this is not my style of music, a lot of guys I build cabs for play these styles of music and use this amp. As far as the clean channel...Peavey wasted money even including it on the amp. HOWEVER....I have to say that the designer of this amp went on to design the 72 coupe for KUSTOM which I own. You wouldn't think much of that being a KUSTOM amp but I'm very fond of it and I think the clean in that is pretty good. Great little amp.

[PRR]

> not wanting to move this thing any more than necessary. I got a little dolly I might try?

Even in my 20s, I NEEDED wheels, usually a hand-truck. Very preferably aluminum.



A trick with this type: roll to car/van trunk/rear, rest handle on jamb, then slide the amp up into the hold.

I usually had a piece of cardboard when hauling CRTs (the aluminum marks-up the glass face), and carpet when sliding amps around.

[Platefire]

Well in my younger daze I manned up to it an manhandled it but these days I've seen to many my age hobbeling around because they overdid it one way or the other. I feel no need to be a Moncho Man anymore. I've got a dolly about that size, not alum, steel.

Talked to the customer today and told him about the only thing I had found with the unbalanced tubes. He told me me to re-tube all or in part--whatever I think. So I'm not sure to stop with just the power tubes? I think these are the original tubes that came in it in the 90's--all Sovtek. Platefire

[PRR]

> stop with just the power tubes?

I'd want to find where the smoke got out. (Of course maybe it wasn't the amp smoking.)

Little tubes generally don't smoke parts.