yann Posted July 15, 2012 Share Posted July 15, 2012 Hi everyone! Back in 2008 i searched for an Mk4,my favorite amp ever built,known as "the tank"... I saw a lot of them,in different conditions and prices,and decided to get this one,"living" in El Paso,Texas. Great condition (except scratches that didn't matter to me),wasn't played more than 4 years, belonged to the dad of the seller (a nice lady),who had an amateur band for this 3-4 year time. Since then,the amp was a "dust collector" up and down the penthhouse... -I saw no rust nowhere on the amp,(the Switchcraft jacks are like new!) this told me that it wasn't exposed to any humidity,then i thought why: El Paso is located allmost in the desert...i thought this is the best risk i can take (buing something used and that old from the net...hmmm!) Costed me more than the double money than buying a european one, plus i needed a voltage converter,and a good service "just in case",all worth it for such a piece! (I did ask Peavey Greece for a change form 110- 220v but they asked for 250 euros plus taxes plus worktime, this would make the amp "golden"...) Anyway,i've noticed that the active channel was in loudness much lower than the passive one, and the serviceman said "it's usual,actives are lower that the passive sects",a thing i didn't believe cause i've worked this amp a lot back in the '80s... A few weeks ago,it really showed whaz up: The active channel started cut offs and scratches,and sometimes going up to the real loudness it should be... After my experience of amp technicians in Greece, i thought to ask for some oppinions or experiences,before i take my loving "Mister Mark" (as the seller named it,and i kept the name) to any "doctor".... Thanks a lot from before! Ps: Anyone has an original footswitch,i'd like to buy it! Quote Link to comment Share on other sites More sharing options...
MarkBassChat Posted July 15, 2012 Share Posted July 15, 2012 [quote name='yann' timestamp='1342352370' post='1733534'] (I did ask Peavey Greece for a change form 110- 220v but they asked for 250 euros plus taxes plus worktime, this would make the amp "golden"...)[/quote]Check which version of the power transformer you have (just count wires on the primary side). Export version has 4 wires and in this case changing supply voltage is easy. [quote name='yann' timestamp='1342352370' post='1733534'] Anyway,i've noticed that the active channel was in loudness much lower than the passive one, and the serviceman said "it's usual,actives are lower that the passive sects",a thing i didn't believe cause i've worked this amp a lot back in the '80s...[/quote]It's rather the other way round - it's good you didn't believe him (is he a serviceman???). [quote name='yann' timestamp='1342352370' post='1733534'] The active channel started cut offs and scratches,and sometimes going up to the real loudness it should be...[/quote]This is quite often caused by dirty Return jacks. Just plug a jack-jack cable from Send to Return jack and see if it helps. [quote name='yann' timestamp='1342352370' post='1733534'] Ps: Anyone has an original footswitch,i'd like to buy it! [/quote]As far as I remember this footswitch consists only of two switches and 4 wires - you can buy any 2-switch footswitch and change the wire (and the plug). Mark Quote Link to comment Share on other sites More sharing options...
yann Posted July 15, 2012 Author Share Posted July 15, 2012 (edited) Mark, Thanks a lot for your reply!! (Mr Mark for Mr Mark huh? ) [quote name='MarkBassChat' timestamp='1342383520' post='1734168'] Check which version of the power transformer you have (just count wires on the primary side). Export version has 4 wires and in this case changing supply voltage is easy. [/quote] This,i can happily do! I'll open the amp soon!(a good reason to clean any dust inside too) [quote name='MarkBassChat' timestamp='1342383520' post='1734168'] It's rather the other way round - it's good you didn't believe him (is he a serviceman???).[/quote] Yes,but he does too many things to be a serious one...(like pickup winding etc...) What i think he really did was finding out that the amp seemed "ok",maybe didn't open at all,and just put new rubbers at the underside.(it had no scratches then,all pots ok too)... He was offently visiting me before that,i was working as a guitar tech that time,and he was always asking about info for guitar repairs,i happily gave,cause i thought it's just two pros talking their jobs,going you know,friendly,but he used this info to do guitar repairs too,along with the amps... [quote name='MarkBassChat' timestamp='1342383520' post='1734168'] This is quite often caused by dirty Return jacks. Just plug a jack-jack cable from Send to Return jack and see if it helps.[/quote] I think that no other jack than the (high) input one has ever been used on this amp,well i've used the line out one for a few tracks of home recording last year! -What impressed me was that the signal was so clean- absolutely no noise,not a little of "hiss"!! I'll check this tonight,right when i get back home!! [quote name='MarkBassChat' timestamp='1342383520' post='1734168'] As far as I remember this footswitch consists only of two switches and 4 wires - you can buy any 2-switch footswitch and change the wire (and the plug). Mark[/quote] I've allready done this with a Vox footswitch,and a plan for it (Mk 3 should work for Mk4 too as said at Peavy's forum i found it) but didn't succeed... (eather the plan was wrong,or maybe the switches other than should be,as i know there's two or more types of them?) It does change channel (switch one) but when the other switch is in "automix" (switch two,both channels) mode doesn't. Must be repushed,then it works.-Plus it makes a noise when clicking! I can't tell if this is normal,never worked the amp with a footswitch,even back in the 80's! Thanks again,and Best Regards! Edited July 15, 2012 by yann Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted July 15, 2012 Share Posted July 15, 2012 [quote name='yann' timestamp='1342387377' post='1734239'] Yes,but he does too many things to be a serious one...(like pickup winding etc...) What i think he really did was finding out that the amp seemed "ok",maybe didn't open at all,and just put new rubbers at the underside.(it had no scratches then,all pots ok too)... He was offently visiting me before that,i was working as a guitar tech that time,and he was always asking about info for guitar repairs,i happily gave,cause i thought it's just two pros talking their jobs,going you know,friendly,but he used this info to do guitar repairs too,along with the amps... [/quote] the cad! Quote Link to comment Share on other sites More sharing options...
MarkBassChat Posted July 16, 2012 Share Posted July 16, 2012 [quote name='yann' timestamp='1342387377' post='1734239'] I think that no other jack than the (high) input one has ever been used on this amp,[/quote]It does not matter whether the jack was not used, or not. It's not about dirt from a jack but rather oxidized metal - it happens also when the jack is not used. Mark Quote Link to comment Share on other sites More sharing options...
yann Posted July 16, 2012 Author Share Posted July 16, 2012 (edited) Mark, it seems like i'm lucky and you're the man! I checked it as you said,and pluged in and out several times, for the first minutes nothing changed,but suddently the sound came and stayed for good all next minutes till i shut down! it's still a little lower than the passive channel,but it shows that after a serious cleaning it's gonna be fine... I'll open up and clean everything devoutly,maybe next week when a couple of obligations are done,i wanna give care and time to it! -I 'd rather let a pro do the job,but i'm a Greek in Greece,i don't know anyone i can trust on such an emotional issue... If it was some "new modell" or something, i wouldn't react like this of course,can always get another one! Thanks a lot, i hope i can do something for you too! Grettings, Yann -Luke, I don't really know what's the meaning of "the cad" here,but i guess you're right!! Edited January 5, 2013 by yann Quote Link to comment Share on other sites More sharing options...
MarkBassChat Posted July 16, 2012 Share Posted July 16, 2012 I'm glad I could help. Regarding the lower gain of the active channel I must admit that I could make a mistatke. Active bass has stronger signal than passive. The preamp for active bass has lower gain than the passive in order to keep the output signal send to the speaker on the same level. Sorry for the confusion - somehow I didn't understand the problem correctly. Maybe it's because I never used active input, or -15dB pad, even when I play with active bass. Most active basses sound better with passive input (unless they have huge signal - then some attenuation is needed - I met only 1 such bass, it was Spector). Mark Quote Link to comment Share on other sites More sharing options...
yann Posted July 16, 2012 Author Share Posted July 16, 2012 (edited) Ok,got it now,no problem! I've never noticed this difference before,just since i have this Mk 4, and i've only pluged two basses in it,both passive,one visible in a pic above,using S.Duncan's "Hawkbuckers" and "standard" electronics (what i own now). Back in the 80s',(using other Mk3s and 4s) i've had one passive (Aria LEB Classic) and two actives (Ibanez Roadstar "Black pearl", and a selfmade one with an active electronic Rockinger has offered for a short period,it even had a headphone output!! ) Can't tell why,i remember i always pluged the high input,with all basses then,and as the amp goes to "automix" if the footswitch is not pluged, i always "made my sound" using both channels in meantime,or just the lower (active one) cause it sounded clearer than the upper (passive) to my ears,hehe... Even in the studio(s),there was no footswitch for both amps (3&4) i've recorded then,so i never really knew the difference,only by the gain pots. Since i got my "Mr Mark",and made that footswitch i heard this difference.but couldn't tell why! Anyway,if there's something really not active in my "set" today...that's me!!! edit: Ow,as i just remembered,that Aria did have a preamp,and a bypass switch,but can't remember how i used it the most!!! Edited July 16, 2012 by yann Quote Link to comment Share on other sites More sharing options...
yann Posted August 24, 2012 Author Share Posted August 24, 2012 It took me a while, till i got the time and mood to open the amp... But it's done,everything in there is as clean as new! Here's some pics: -73,-74.Quite dirty in there,back panel open. -79,-82.Front panel open and dismantled. -84,-85.If you ever open this amp,mind that the left plastic frame is not removable,as the right one (eq section) is. -86.Job done,all tools i used. (one more post coming) Quote Link to comment Share on other sites More sharing options...
yann Posted August 24, 2012 Author Share Posted August 24, 2012 (edited) Pics -89,-90: My 110v transformer,it seems like a 3 wire one...(3 + 3) -After finishing the job,i remembered i didn't get some closeups of the transformer,so i opened again,well,just 4 screws.... Then,was the test time... i pluged and turned on,sure that everything is clean and it's gonna sound just right. Guess what.... Nothing has changed. The noise and cuts still there,even if i looped the send-return,and in a few minutes it worked ok again, just like the looped test i did before,but it wasn't the wiring that made the amp work,but the warming!! Now,i think it's something that doesn't work when cold,but comes alive after the warm up.... I don't think it's something i can find and repair myself,i'm good with mechanical parts, but not with electronic elements,that's a pro's job now.... -Mark,thanks again for your help,the problem might be deeper than dirty jacks,but you gave me the guts to open and find out more..! Edited August 24, 2012 by yann Quote Link to comment Share on other sites More sharing options...
MarkBassChat Posted August 25, 2012 Share Posted August 25, 2012 (edited) Regarding the transformer: the photo is not perfect but it seems that you have 2 secondary windings (3 red and 3 orange wires on the right) and the primary winding has only 2 wires (black and blue wires on the left). So it seems that this is US domestic version (117V) - you have to buy a new transformer, or rewind this one to use it with 230V mains supply. I think that rewinding shouldn't be to expensive - you just have to find out someone who can do it. The other problem requires some understanding of electronic schematics. If you cannot fix it, give it to a tech. With Peavey similar problems are often caused by non-contacting plugs. You can check every plug in the amp whether it's not oxidized. You can also investigate the problem a little bit more; you can check whether the problem is related to the preamp or the power amp. I'm sure that there is power amp input jack; by pluging there an external preamp you can check which part of the amp fails. Mark Edited August 25, 2012 by MarkBassChat Quote Link to comment Share on other sites More sharing options...
yann Posted August 25, 2012 Author Share Posted August 25, 2012 (edited) Mark,i guess you're right about the transformer, i think i just let be,since i ain't no active player no more, so i don't have to carry the 220-110 xtra transformer i allready have!(it's very heavy,and an xtra "box") About the other problem,it's pre-amp for sure... It only happens with the active-eq channel (lower),while the passive-eq one (upper) works fine from the first minute (high gain plugged). -Hmmm...about contacts as you said,i just thought something i didn't before: The footswitch jack!! I didn't pay any attention to it,and haven't plugged it for some months...it's "contacts" too,ain't it? And it's a quite sensitive element as known from the history of those "stoneage" jacks! Otherways,i'm gonna have to check all those little chips of the front panel (they're all in sockets,contacts indeed), well the ones that seeme to belong to the lower channel where the problem comes from... I think i wait for the right mood,and check it out,opening the amp again is nothing now that i know the process and what's in there! EDIT: One thing i gotta clear up here,so readers won't misunderstand: -When i talk about "active" and "passive", i don't mean the inputs (high and low gain,used for passive or active instruments), but the EQ sections!!! In this amp,the upper channel has a (so named) "passive EQ" (the ones starting from 0 hard left to 10 hard right), and the lower channel has an "active EQ" (with 0 in the center and + - 10). So,Mk owners talk about "passive channel" and "active channel" meaning the EQ sections,not what's plugged in!! Edited August 25, 2012 by yann Quote Link to comment Share on other sites More sharing options...
yann Posted September 2, 2012 Author Share Posted September 2, 2012 Ι did a first check... Plugged the footswitch in,and switched the amp on... well,the active channel (lower) was crystal clear this time,but the passive (upper) with a bad "hiss"... Torn the amp off,sprayed some (no oil) contact spray in this jack,took the footswitch plug in and out a few times (turns both channels on in automix mode), let dry,turn on again,both channels clear too.No noise at all anymore. (but the -non original- footswitch doesn't work well since it's made anyway....) Focusing at the footswitch jack now... Quote Link to comment Share on other sites More sharing options...
vaccastracca Posted October 12, 2012 Share Posted October 12, 2012 Hello everyone. Sorry to burst in, but since I just got the same head, and I'm having some similar problems, I thought I might share the experience, in case someone has some tip! I write from Italy, and like Yann, I don't like the idea of giving the Mark IV to a technician...in my case it's not a matter of trust (I trust my tech), but it's just he's terribly expensive, so I usually go to him when there really is no other chance! Here is the issue: the graphic EQ, when engaged, causes a HUGE loss of volume. We're not talking of a few dB. It goes down to less than half of the volume you're using! Besides the volume loss, the tone also becomes very muddy and dark. The issue is the same on both channels. Other than this, the amp works totally perfect in every aspect, and sounds awesome. Quote Link to comment Share on other sites More sharing options...
yann Posted October 12, 2012 Author Share Posted October 12, 2012 [quote name='vaccastracca' timestamp='1350048498' post='1834012'] Hello everyone. Sorry to burst in, but since I just got the same head, and I'm having some similar problems, I thought I might share the experience, in case someone has some tip! I write from Italy, and like Yann, I don't like the idea of giving the Mark IV to a technician...in my case it's not a matter of trust (I trust my tech), but it's just he's terribly expensive, so I usually go to him when there really is no other chance! Here is the issue: the graphic EQ, when engaged, causes a HUGE loss of volume. We're not talking of a few dB. It goes down to less than half of the volume you're using! Besides the volume loss, the tone also becomes very muddy and dark. The issue is the same on both channels. Other than this, the amp works totally perfect in every aspect, and sounds awesome. [/quote] Hi, it was about time for my news too! Well,my one goes fine,the trouble is spotted at the footswitch jack, that works as a contact too,and is fixed since my last post here! It was a contact causing it at last,thanks Mark! vaccastracca, I'm not sure if i can help here,i don't know much about electronics... What i know is that the eq section of this amp is a serious tool,very usefull when changing playrooms or stages. The eq goes "on" with different switches for each channel,you don't mention any difference between them,so i can guess the loss ain't caused by one of them...next thing to check out is the eq sliders,i think if one goes bad affects the others too. But this is just the "mechanical" side of the story,i can't tell if there's some electronic element that's bad,i would get to a pro too with such an issue... Still,it's no thing to check the sliders,clean up with air preasure first and plenty of contact (no oil) spray...(dont worry if it runs everywhere,just let dry). Anyway,if you're doin good with screwdrivers and things,take a look at the photos above,and go for it! A general cleanup is never bad for an amp!Have fun,and...good luck!! Quote Link to comment Share on other sites More sharing options...
vaccastracca Posted October 12, 2012 Share Posted October 12, 2012 Thank you very much for the prompt response to my message Yann! :-) Today I could phone a very good tech i know (unfortunately he lives 600km from me so i cannot bring him the head)...i described him the situation and he said it sure is a faulty integrated circuit in the preamp section. Cheap part. But lot of work to get it changed! Which translates in a "lot of money to spend" if i bring it to any tech in my area! So I'm considering the option of disassembling the amp by myself and maybe try to change the faulty chip with a friend of mine who is very good with soldering instrument parts etc... I carefully inspected your pics, and it looks it's really a big task to disassemble this amp!!! I guess the preamp section is in the front...which disassembly-order should i follow to take the frontal part out? ...it seems there are many small parts to take out one by one...and what I'm most worried about is the chance of unintentionally stretching some cable and maybe even breaking something!!! Quote Link to comment Share on other sites More sharing options...
yann Posted October 12, 2012 Author Share Posted October 12, 2012 (edited) Hmm,maybe your tech has seen (heard!) this before, a pro does a lot of things every single day...that's how pro's gain experience! -Your good news is the chips in there are all in sockets as they look like, just pull out and install the new one (with care of static electricity). -Your bad news is you don't seem that confident for such an operation... Doing such things is always a risk,you gotta like risk first! (not on things that belong to others of course!) Well,it's a beat of work to open the front panel,4 screws up and down,8 at the frame to release the front from the box, plus all the bolts of the pots (behind the buttons!!) and jacks to split the front from the cirquit. Good care when pulling out,theres cable sockets at the back of it. More care when assembling,watch out the torque you tight your bolts,this ain't no car or bike! Good luck whatever you decide! Edited October 15, 2012 by yann Quote Link to comment Share on other sites More sharing options...
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