Chat about Equipment Info
 #86125  by waldo041
 Thu Sep 02, 2010 7:32 am
tracy,

don't know if that mc250 is stock, but if it is, those are some 30+ year old electrolytic capacitors in there and should have been swapped out 15/20 years ago. you more then likely only need to swap out the electrolytics in there, and may consider sending the multi section cap can out to frontier electronics for a servicing before everett retires. the other single cap can, can be bought at audio classics. if your doing the job yourself, SOLDER SUCKER AND SOLDER WICK are your friend. those pads will lift if you heat them up too much. so be in and out as much as possible with the heat.

replacing those caps with better quality, longer lifespan new ones will get you another 30+ years out of that amp.

peace,
waldo
 #86127  by JonnyBoy
 Thu Sep 02, 2010 7:55 am
I am gonna give my 250 a recap, I know there is nothing around here where they specialize in Macs. Plus, with shipping it costs way too much to send off. This should actually be easier than working on the TRRI.

Are there any Electrolytic caps that one would want to change to drops or film? I am not advanced enough in amplifier construction to know what would be a better choice.

Waldo checked out frontier, couldn't find it, u got a link or a # ?
 #86155  by modz
 Thu Sep 02, 2010 5:51 pm
I'm looking forward to the steel guitar convention, I will be there Friday. I took the bottom off looking for obvious signs of trouble, bulging caps, fresh solder etc. I didn't see anything that stood out. It's really quiet though! no scratchy pots or pops.
 #86158  by modz
 Thu Sep 02, 2010 6:15 pm
waldo041 wrote:tracy,

don't know if that mc250 is stock, but if it is, those are some 30+ year old electrolytic capacitors in there and should have been swapped out 15/20 years ago. you more then likely only need to swap out the electrolytics in there, and may consider sending the multi section cap can out to frontier electronics for a servicing before everett retires. the other single cap can, can be bought at audio classics. if your doing the job yourself, SOLDER SUCKER AND SOLDER WICK are your friend. those pads will lift if you heat them up too much. so be in and out as much as possible with the heat.

replacing those caps with better quality, longer lifespan new ones will get you another 30+ years out of that amp.

peace,
waldo
Thanks brother. I'm doing a lot of reading and have some experience with electronics. I'm looking to buy a scope and I am going to get into this side a little more. I just want to understand my amps. I've been bugging Sarno since 1989 and he hasn't punched me in the eye yet so he is going to take me through some basics. Is the multi section cap the silver caps in the front? I found this tidbit and I'm sure it's obvious info for most people here but for any newbs you should have a gander at it.
http://6streetbridge.blogspot.com/2008/ ... pdate.html
 #87382  by modz
 Fri Oct 01, 2010 3:46 am
So I brought my MC250 to Brad and he put about $10.00 worth of capacitors in it for me and it kills now! Such a big difference. Big thanks to Brad. I used one channel at the Tuesday Schwag gig and it was so nice. LOUD TOO! I'm glad I didn't sell it now. Thanks for all of the input.
 #87392  by JonnyBoy
 Fri Oct 01, 2010 8:50 am
modz wrote:So I brought my MC250 to Brad and he put about $10.00 worth of capacitors in it for me and it kills now! Such a big difference. Big thanks to Brad. I used one channel at the Tuesday Schwag gig and it was so nice. LOUD TOO! I'm glad I didn't sell it now. Thanks for all of the input.

Would love to know what Brad did specifically, or at least which parts he thought needed to be changed out....
 #87395  by SarnoMusicSolutions
 Fri Oct 01, 2010 9:38 am
I replaced all the electrolytics except for the two large GE cans. Those things seem to hold up pretty well after all these years. Also, they're real pricey to replace, at least $20 each at the bare minimum. Not real pricey I guess, but way more than all the other cap's put together.

What I did was leave the two silver smaller can's in place, but inside the amp I disconnected them. The replacement cap's of the same values are SO much smaller than they used to be, so they all fit very nicely inside there. The only trick was the silver can closest to the front of the amp is actually a single and is for the negative supply. That cap's polarity was a bit confusing at first when looking at the amp because the + side goes to ground. Electrolytic polarity is CRITICAL because if you reverse them, they are like a dead short and things can fry real fast. Plus they can pop or at least smoke and ooze some nasty liquid.

Also, the 2 10uF cap's on the input board are for coupling audio, so I used poly film types instead of electrolytic since film is a far superior audio coupler. I didn't quite go to 10uF, but went 2.2uF instead. Still plenty of bandwidth there, and for Jerry style guitar, not an issue at all. I believe that some of the Mac's even used to use 2.2uF there instead of 10uF.

At first Tracy's Mc250 bench tested about 63 watts on one channel and 68 watts on the other. Kind of mushy and sluggish compared to what it should sound like. After this re-cap job, both channels were delivering a solid 82 watts per channel right at clipping. This particular Mc250 of Tracy's was by far the cleanest circuit I've seen in one yet. Outside had some metal pitting, but inside, I swear this amp had never been abused or even opened up before he got his hands on it. Every component was stock, zero charring around the Sentry Monitor resistors as we see in most used Mc250's. This baby came right back to life with tons of clean power. I love these amps.

Brad
 #87409  by JonnyBoy
 Fri Oct 01, 2010 10:59 am
THANX Brad!! That is what I was after... You would love mine too, I opened it up everything stock and everything pristine. no burns either. It is doing the same thing as Tracy's, I know it can be louder (my Mc50 blows it away, but it was re capped before purchase) I will be putting a mouser order together here soon.

One of the sides goes out completely between 5 on the vol pot to about 8 then back in with sound as you turn it louder. No scratch to the pot, just no sound from 5-8, as if there were numbers on the amp to evaluate. You think its a pot or just bad guts, or maybe you can't tell without seeing it. At least it cranks full blast, but I know it can be a bit louder. AGAIN thanks for your knowledge and sharing it with us... JB
 #87415  by mijknahs
 Fri Oct 01, 2010 11:24 am
If the pot goes out only from 5-8, it sounds like a bad contact in that pot (bad pot). Maybe it can be cleaned but probably needs to be replaced.

Jim
 #87478  by JonnyBoy
 Sat Oct 02, 2010 1:30 pm
mijknahs wrote:If the pot goes out only from 5-8, it sounds like a bad contact in that pot (bad pot). Maybe it can be cleaned but probably needs to be replaced.

Jim

Thanks Jim I was thinking that, It won't hurt to replace it. I wonder what kind of pot it needs.
 #88843  by modz
 Tue Nov 02, 2010 10:09 pm
Switching to a mc2300. My back is going to be hurting! I found a good 2300 and the guy wants 900.00 so I'm going to sell my mc250 to get it. I love the sound but I want some more headroom. I'm loud:)
 #93082  by mijknahs
 Tue Feb 01, 2011 5:49 pm
modz wrote:The guy with the 2300 backed out:( He came to me asking for a 2x12 cab and 500.00 bucks. Oh well the 250 sounds great so I will keep it!
How does the 250 sound bridged? You should be getting around 160 watts bridged. Is that how you've been running it?
 #93083  by Pete B.
 Tue Feb 01, 2011 6:06 pm
fwiw, I now own that specific MC250, but haven't run it "bridged" yet.
 #93086  by mijknahs
 Tue Feb 01, 2011 7:25 pm
Pete B. wrote:fwiw, I now own that specific MC250, but haven't run it "bridged" yet.
Right on Pete.