Peavey 6505+ Repair, Settings, and Testing
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- เผยแพร่เมื่อ 22 ส.ค. 2012
- Documentation of repair, settings and testing of Peavey 6505+ head. I could not get the power amplifier to meet its specs until I corrected the filament voltage issue. Apparently, the PC board runs are so thin that the drop across the paths adds up to 0.6 volts by the time it gets to the PC board with the 6L6's. Also, front control settings are critical for providing maximum output with desirable overdrive and effects. Hope this helps.
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i am goin to order a new set of 12ax tubes this week. thank for your help so much.
just a little tip from a guitarist point of view (and amp tech myself):vintage amps like Fenders and old 4 input Marshalls were not really intended for big distortion,it happened but at high volume,you know how.
Modern amps like this are created with much more distortion in the preamp,cascading stages,mid boost eq etc.,even the clean channel could have a milder harmonic distortion to achieve a thicker more "chorusy" sound,all of this in a fairly clean output stage.
About EQ,almost every guitar amp has a tonestack which is never linear like a hifi amp,if you put every knob on 5.
The only amps with linear response are Ampegs (some) Carvins and few others
Old blackface Fender have a big mid scoop while Marshall tend to have apparently more mids,that's why they distort easily,in general.
I liked all of your videos,thanks for the information you provided for free.
Any info you need on modern amps and techniques involved,i'll be glad to help!
Alessandro
Alessandro - Thank you very much for this information. Even though I am not a musician, your descriptions help expand my knowledge of music amps. I find the Fenders and Marshalls the easiest to work on and verify "proper" operation as, in the end, I tend to want to make the amp perform at it's stated power level at about 10% THD. That may not be the best test but it's about all I can do. The more modern amps as you describe them definitely have initial gain stages that are not linear and even a few millivolts will drive them into tremendous states of distortion and I can see you know this as well as I do and even more so as a musician. I do these videos because it is a hobby and it just seems right for me to give away something that costs me nothing to create and may help others - Thank you for your generous offer, I may have to call on you for advice.
MrAletube can you help me diagnose my 6505+? squealing on the rhythm channel at low volume and gain. all preamp tubes have been replaced.
Can you swap in a spare 12AX7 one at a time? The simplest of problems can sometimes be the hardest to troubleshoot as we overlook them. A good visual inspection might reveal a broken wire or a contact not making -then of course it could be a relay or something else and become more complicated - do you have a good tech close by you can take it to?
The solution for the low filament voltage was to add wires parallel to the PC board runs so that proper voltage was on the filament pins of the 6L6's and the solution to the front settings was to set the knobs as shown on the Peavey website as per the pictures that they provide. Hope this helps.
Since you will be setting the bias at a static level, you should be able to use any high Z meter unless I am missing something here. The FET meters built by, for example, Heathkit in the 70's were extremely sensitive to RF and would self destruct in the presence of low levels of RF by destroying the input FET. If you have to adjust under drive maybe a vintage General Radio (Genrad) or such? Do you have a plate current meter in the RF section you can use to adjust plate current? Hope this helps.
cool vid. any idea of how to determine if my footswitch for a 6534+ or amp has issues? footswitch will light up rhythm channel and solo but it will not switch to rhythm.. I get clean and solo channel only. but all channels work with out footswitch plugged in
Thanks for the fast reply. Yeah I just found a good tech im taking it to him today.
Btw love all amp vids and im trying to get into fixing tube amps myself. I fix guitars now but need to know a little more on tubes. I was wondering if you should show a video of how to properly drain a tube amp. I've searched all over the net and no-one gives a live run through. Seeing as most people don't know there is a lot of stored power inside of tubes amps that could possibly kill you. Please :D
There's any addressing for the pre amp valve for the channels? like.. clean channel use some valves and the lead use the others valve? Cause im having these problem, that when i use the lead channel, the sounds cracks...
Nice video !
I appreciate all the time you have spent on this, but the lowering of the voltage to the power tubes on EVH version of this amp is by design. The 6L6 power tubes sound different when the filaments are starved. Read about the EVH "Brown Sound". This characteristic was retained in the 6550 version of the amp. You can read more about it here - www.legendarytones.com/brownsound.html
Not saying that isn't true (and I didn't read the article yet), but that really doesn't sound right if that's how they did it. The brown sound mostly comes from a diminished plate voltage, not filament starving. That's why some builders (i.e. Metropoulos) use dual winding B+ tap power transformers, so you can get the brown sound on a switch without starving filaments and burning out your tubes faster. Idk, just a thought.
Are these two cables "mod" fixing the volume/tone drop on the fx loop? Thanks.
what would make the presence and resonance dials stop working? i picked one up used and sounds great but the presence and resonance dont work.
What where the initial complaints from the owner? Or how did the amp function (or not function) before the repair?
i need some advice on where to work on my peavey 6505. i have feint volume in my amp, that is being controlled by my pre channels, my post, output volumes have no influence or change any level of sound when turned in any direction. would this be a voltage problem?
It is hard to say but maybe one of the filaments is out in one of the 12AX7's - turn off all the lights and check that there are two (2) filaments lit in each 12AX7 - also, possibly a bad connection in one of the jacks because if you have a Send and Return they are connected together internal to the amp through the quarter inch jack when nothing is plugged into them. Plug your guitar straight into the Return and see if you get anything - won't be loud but that bypasses all the preamp section.
HI and love the technical way you take to that peavey 6505+ head which i have, i'm from south texas Mcallent area, sometimes called the rio grande valley if i was to take an amp to u how long would it take to test it and maybe replade the power tubes and check the preamp tubes to make sure everything is working, i found mine at a pawn shop and it has groove tubes gold i think, let me know thank you again for such an informative video, ;)
alright, first i inspected the pre amp tubes, (note i had bought this amp used couple weeks ago) there are two (2) tungsols and three (3) jj tubes. the tungsol filaments are very dim compared to the jj tubes. second i plugged straight into the return, and i almost blew my ears and probably woke my neighbors : D. so i conclude that your assumption on a bad jack connection is the problem. i shall await your response before proceeding.
I have the same problem, did either of you find a solution?
Hi, good video.
Do you know if the Peavey loop is serial or parallel? Thanks
Danilo Zolet serial
I have the same problem, did you find a solution?
By the way it does play through the "return" jack on back only
Can you tell please which tube is the V6, I'm going to change this to a Balanced Phase inverter 12ax7 from JJ tube
Here is what I found - I cannot verify it without a schematic which I cannot find - hope this helps.
V1A - Input for both channels (1st gain stage)
V1B - 2nd lead gain stage
V2A - 3rd lead gain stage
V2B - 4th lead gain stage
V5B - 5th lead gain stage
V5A - 6th lead gain stage (driving tone stack from the anode)
V3B - FX loop driver for both channels
V3A - FX loop recovery stage for both channels
V4A + V4B - Phase Inverter
V6A - 2nd clean gain stage
V6B - 3rd clean gain stage (driving tone stack from the anode)
Fix my Peavey 6505+ please!! Some tech screwed mine up.
**It plays nice and sounds nice but all of a sudden the level will turn down by its self, make a little click then come back to full power. Its a weird problem. Its not always their either., Sometimes i can play a full set with my band and have zero problems. I have replaced all tubes also. Ive done everything i can on my end. My clean is also super quiet and has no bite to it. Once again all tubes are replaced. Please help.
I bought a used 6505+ today and everything seemed fine until I got home with it and really tried it out. Since I will mainly be playing on lead channel that's the thing I put the most effort into tweaking around with. However, when I decided to try out the rhythm channel I found that the volume was way cut and turning the post-gain all the way from 1-10 did almost nothing to the sound, it was comparable to having it around 1 as it was supposed to be. Neither the bright or crunch switch had any effect on the clean sound. I then tried to turn it off and without knowing how (I suspect I switched to rhythm channel before turning it off) when it went back on the rhythm channel now gave me the volume it was supposed to be doing but the bright and crunch still did nothing. Now here's the strange thing, when I finally thought it was just something that needed a restart, when I changed to the lead channel this time it was behaving like the rhythm did. Very low volume and almost no distortion. So I turned it off while in lead channel and turned it back on and now it was reversed. After I got home I found out that I had put my amp head to 8ohm and discovered that my cabinet was 16ohm. Can this has anything to do with it? I first thought it had to do with some pedals I ran through the FX-loops, but taking them out and running only the guitar straight through the amp made no difference.
I'm really poorly educated in amps and I'm sorry for any grammatical errors since English is not my native language. I would just like to know what the problem might be and if I need to turn it in for repair. Thanks!
It has been a number of years since I worked on this amplifier but I do remember it. I am not a musician so as a tech I always want to test the amplifier at its maximum power output after working on it.
I remember having a very hard time getting all the knobs set so I could get maximum power output.
I had to look on the Internet for the exact knob settings and when I duplicated those settings I got a lot of power out of it.
You may be able to look at my video and set your amplifier knobs exactly as I have them set when I measure the power output. After the adjustment for maximum power output, adjust each one carefully so you can return to a good operating position.
I hope this helps.
Hey I'm having an issue with mine, Its extra noisey for no apparent reason. I unplug everything from the amp just leave it power and hook it up to my cab turn it on and on all 3 channels I get a mix of 60 Cycle hum and a "ehh" sound (It gets worse as I go from Clean- Crunch-Lead) any Ideas what it could be? I Taken it apart and everything looks in order (no broken Fuses,car and resistors look fine, all the solder joints look fine) Sprayed it down with some Pc board Cleaner and the noise went away for a bit... plugged it in after letting it rest for 5 hours and the noise is back! any help would greatly appreciated thanks!
Those kinds of problems can be tough to find but the good thing is, it is probably something pretty simple.
I assume you have removed each tube and spray cleaned the socket with contact cleaner. That could be it.
The vibration of the cabinet can cause small cracks and damage parts that are pretty much impossible to see with the eye.
With the amplifier off, I might remove the first stage tube - probably a 12AX7 or 12AT7 and power it back up and let it sit for a while. Tapping on it here and there on the tubes and chassis That might help locate the source of noise. If that shows nothing you can most likely eliminate the first high gain stage which can be a real problem. Clean and examine the 1/4 inch input jacks. You can continue this one tube at a time and see if pulling one stops the noise. It will take some time to do this so be careful and take notes which tube(s) are in and out. It could be a coupling capacitor breaking down and this would be harder to find - and it does happen - but this process could get you closer if not solve, the problem. Best of luck and I hope this helps.
What type, brand of meter, would you recommend that I can use to set the bias on some RF Amp tubes?
This is a prettyold post but a good one--veryhelpful.. I am wondering if your still available--I am trying to repair having my issues. Thanks
if theres one thing ive learned from owning this amp is it has teeth, very large sharp ones at that, its meant for devouring tones. not a great amp for the light hearted how want to pluck and fancy acoustic sounds with no distortion. my 6505+ is a monster and it has a very nice edge for hard distortion levels, thing is, it took me a while to tune in my tone, get things nice sounding on all spectrums, a good speaker cab also is the defining part. a nice Marshal 1960 with Greenbacks is my choice for a mate.
I wish you had a video on the mod that you did kind of a mod so I can have mine check to see if it needs to be that way
I am in El Paso, Texas.
The reason I made this particular video is because in testing most amps - Fenders, Marshalls, etc, I just set all controls at 12 O'Clock (midway) and adjust the input drive and can get full power out with 10% THD or less. With this Peavy I found it a bit more complicated and had to adjust to some Peavey recommended settings to get full power at about 10% THD. Not trying to say there is anything wrong with the amp but it is not as simple as some of the other vintage amps I am familiar with.
You definitely found out something there - the problem is not in the output section. Your issue is before the Return jack either in the preamp section or the jacks themselves. Google your amp with 'schematic" added and it will pop up. You will see in the lower right hand side of the schematic the Send and Return jacks. Lots of simple things could be the problem - the jacks have a tab that feeds the signal thru when nothing is inserted - that may not be making contact (next post)
120 watts? Peavey is dreaming! Lucky to see 85 watts from a rig like this, unless they over volt the power tubes.
The notch distortion indicates high plate resistance. Too much negative bias. Reduce the negative bias a bit and the sine wave will clip clean without the notch, as has been my experience with a recent Fender Twin with four 5881s.
my pre-amp tubes do not come on so I replaced them as per Peavy's techs, still are dark and I get no sound, am I missing somthing?
I can't remember every amplifier but I think there is a filament fuse under the chassis that is blown. A 10 amp if I remember correctl
+ElPaso TubeAmps Why such a big fuse, just curious and reading this info the first time, peavey has really changed their amps since the 70's.
A little click or clicking sound makes me think a relay is turning on or off making it switch channels. These types of problems can be a challenge. i am sorry but I have no definitive suggestions as to what it might be. Hopefully, you can find a compentent tech in your area willing to take the time to fix it for you at a reasonable price.
this is very interesting. My 50w 6505+ cannot pass a clean sine wave through the clean channel. It looks healthy after the first common gain stage (V1a) but looks quite crappy (all kinds of spurious garbage, not just clipping) at the following volume control before V1b. My power amp section sounds good. But I cannot figure out why my preamp is turds.
Furthermore, if using a sine wave, using passive lossy non-resonant filters such as found here, should do nothing but possibly attenuate the sine wave, not change it in any way. But there appears to be other crossover distortion and bad harmonics at work in my preamp.
jhelmwaterw I understand and found it "interesting" that I had to go to the Peavey website to find how to set-all-the-knobs to get it to pass a clean signal - good luck.
I assume the V6 is the Phase inverter thank you, LOBO
wish you would of demo the sound after repairs made.
A mod that I do on this amp all the time is I take out the on meg grid leak out for the clean channel in replace it with a 68k
Also a 62 k works just as well!
I assume that reduces the gain and calms it down considerably. Probably a very good idea. Thanks
there is not a techy close by. nearest serice center two hours away.
what would cause one of these amps to give a loud hiss. volume controls do nothing to change it. it's just a loud ass hiss.
First impression (just starting the video): The preamp section does NOT look well-ventilated
I can just imagine what a temperature rise will do to those PC boards - PC boards and tubes do NOT mix! :)
David Perkins its fine. The tubes don’t get anywhere near as hot as the power tubes. The reason they are encased is because that head is built like a tank. Ive tackled mine (it was on top of 2 cabs, and it survived the fall.
Squealy 6505+ Part 1
10% distortion? Ah, no wonder. Likely the HONEST unclipped power out is under 100W.