Mark IIC+ repair. Need help!

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Boogier

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Hi guys

I just bought a mark ii c+ and love it. It was shipped to me ground, and took a week to arrive, so I assume I was riding on a truck for a week. It worked well for about 2 days. Then the crackles started. At first it would crackle at startup for about 10 minutes, then after about 3 hours. Then it would only crackle at startup and after an hour. Eventually it crackled every time it was powered on. I bought new tubes and installed them. No differemce. I should also mention I swapped the speaker.

So I took it to my usual repair guy, and here's what he did - 1. Gave it a good once over, including fixing a loose/falling apart solder joint in the V1 socket. 2. Swapped V1. It didn't crackle at his shop. Of course I got it home, crackled immediately the next morning. Called him back then took it back. He then 1. Swapped both power tube sockets. 2. Re-tensioned the preamp tube sockets. 3. Gave all the tube sockets a good cleaning. 4. Replaced one cap. Not sure which one.

He had it on at his shop for two hours with volume at max through his own speaker cab - not a single crackle. I thought it was fixed - after an hour of use began to crackle.... took it to a local big repair shop. The guy there didn't seem like he knew what it was either....

So I'm looking for either a diagnosis I could call this guy with to help him, or a good boogie repair shop in Chicagoland. Help!!!!
 
I had similar problems with crackling, If you look at the thread of mine "Mark III died again" you go to the last page and check out what was wrong with mine, sounds very similar - it ended up being a blob of Solder under the V2 pre amp valve socket - had to pull the board to see it, but that in fact was the cause of the crackle. Mine would do it on start up - and sometimes when loud palm muting heavy riffage playing at volume - anyway - I don't know if that will be your problem, but It was mine, worth a look anyway

Casey
 
HI kc - I looked on here (seems to be lots of these problems with the older mark series?) but didn't see your thread. And you're right, this sounds like the same type of problem. I will definitely tell my tech about it. I have compiled a list of possible culprits - the tech is gonna hate me!

and xdg - the 100 watt with reverb no graphic EQ iic+ is the one I was looking for! if you ever want to sell one locally in Chicago without having to ship (damage!) it, please please please write me a private message. I looked for one online for months and got sick of looking and got this 60 watter. It's not enough power (yes i know its a lot) but I need LOUD clean clean. Really, please write me.

Thanks for the help so far guys - any more help would be greatly appreciated!
 
I won't be selling any of my c+'s anytime soon. It took years to find another HR combo. I'm actually looking for another HR to add to my collection. The guy I bought my DR combo from last fall still has 5 c+'s. And I thought I had a problem! :)
 
That sounds def intermittent and equally poss electronic OR mechanical in aetiology..

U/someone NEEDS to narrow down the error area ie: V1, V2, V3 etc etc etc etc.. and which channel.. or both...
Some random thoughts without chassis on my bench...:
Assuming all voltages are in spec and STABLE, without ripple, at least verify a preamp or poweramp source. This is imperative to not waste a lot of time and/or money. Or both.
If power, clean the hell outta board and sockets. Check leaky coupling caps. Check screen grids not breaking down (not uncommon with heat and age or a dying 6L6 frying them..)
If pre, check failing carbon comps, (CRO +/- chopstick/tapping), crud ANYWHERE from input jack forward. Check all earths ESP jacks. Again, leaky coupling caps - spurrious DC can crackle but constant gives humm..
Check DC BETWEEN tracks.. - one of my Mk II's and my Kitty Hawk M1. Complete ******* to find..
?Failing LDR's? CRO will show quickly and easily..

Re KC's solder blob - the IIc sockets come UP through the board. No blobs. AND board is 99% single side

And usual checks - fx jacks, crud in pots, DC on pots, dry joints esp in high heat areas, rev jacks, eq sliders..
The list is long hence narrow the area ASAP..
There's some ideas to drive yr techs a bit crazy.. They'll have their own methods but I've seen all of the above..
As always, pls post results for future readers..

Cheers, Dave
 
hi guys -

its back and its working! i'm excited. its sounding great.

he told me there were a bunch of solder joints that were suspect (didn't tell me where and i was so excited to get it back I didn't ask...) and changed some plates having to do with v1 and v2. Again, kinda excited and don't know much about plates.

If anyone needs this info i can call back and ask - just PM me.

Again, thanks for the help guys!
 

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