Tom Mitchell - Mitchell Pro 100

[xtian]

I decided this amp is a keeper. So I'm recovering the cab. Look what I found. Any comments about "rat-shit tone" will be acknowledged as the absolute truth.

Repair person, "Oh, I see your problem, right here."

[pdf64]

The static dissipation of the power tubes and the audio power output of the amp are different things, don't get them muddled up.
Pete

[xtian]

The static dissipation of the power tubes and the audio power output of the amp are different things, don't get them muddled up.
Pete

True, dat, Pete. Thanks.

[xtian]

Sexy in black, before-and-after photos. It was FUN pulling out all those upholsterer's nails!

[Structo]

What is the new grill on the black one?

I like the looks of that.

[xtian]

This:

http://www.mcmaster.com/#9344T55

It looks nice, but at 20 gauge, it's far too thin and easily bent to be practical in general use.

[SkOrPn]

I sure hope this isn't against any rules but I found one of these Mitchell PRO 100's in the attic today. It says Mitchell PRO 100 on the front of it but I did not touch it because of the dust on it. Will clean it up later if I can figure out if its worth it or not. I vaguely remember back in 1997-1998 taking guitar lessons with a fellow employee who worked with me at an Electronics Manufacturer (I was an Intel QC/QA Tech back in the late 90's). After work he and I would spend an hour or so teaching me to play the guitar. The lessons only lasted about year, if that. I am a natural country singer, but love music in general especially rock from all genres and country. In the 1980's I was a lead singer for a rock band in Albuquerque, NM but that too only lasted about a year. Since the late 1980's (89) I have been a Electronics Technician and then since 2001 a Computer Tech, so music just seemed to take a back seat and unfortunately I never really learned to play the guitar. Not to mention I discovered I simply can't remember lyrics by heart, even if I write them myself, which sucks haha.

Anyway, I am trying to find things to sell on ebay/craigslist and take to the dump anything we don't absolutely need, and today going through the attic above our Garage I came across this very dusty Mitchell PRO 100. I remember the guitar teacher had owed me some money, can't really remember how much but I vaguely remember it was around $150, so since he never could pay me back he gave me this instead. And lol it just sat in my attic since then of course. The amount of dust on it, well its about 15 years worth easily, haha.

Can someone tell me if this would be worth cleaning up and selling on Craigslist or eBay please? Or is it worthless and I just take it to the dump? Since I am an electronics tech, is there something I can do with it to make it more valuable and worth selling? How can I test it without a guitar?

I believe this is the unit in the video below, but I do not know anything about it.
http://youtu.be/r2wV1zaz3Lw

Any ideas what I should do with it would be appreciated. Again, please accept my apologies if this post is an intrusion. I just don't know where else to ask. Maybe I will call a music store and ask around? Thanks for any ideas on what I should do with it.

Best Regards
Rod

[tele_player]

The common formula for 'RMS power' is Vrms squared, divided by load.
Depending on what the transformer expects for a load, 100W would be about:
56v P-P into 4 ohms
79v P-P into 8 ohms.

-robert

I fixed some minor issues and gave the amp a good workout. Damn. Loud. And very fine.

I put a 1kHz sine at the input, and I can get 32v p-p at the output just before clipping (against a 4 ohm load), and it's a nice, sine-shaped wave, too. I found various formulae to convert to watts. Some say, p-p x 0.707 (RMS), but that gives me 128 watts. Some say p-p * 0.637 (average), and that gives me 104 watts, which seems likely, because this is a 100-watt amp.

However, then I found this paper: http://www.dytran.com/img/tech/a13.pdf
...which says average value is not peak-to-peak volage, but only peak voltage (half of p-p). But this gives me only 26 watts.

Is the method in bold actually correct and I really am measuring 104 clean watts?

[Leo_Gnardo]

I found one of these Mitchell PRO 100's in the attic today. <snip> Can someone tell me if this would be worth cleaning up and selling on Craigslist or eBay please? Or is it worthless and I just take it to the dump? Since I am an electronics tech, is there something I can do with it to make it more valuable and worth selling? How can I test it without a guitar?

Rod

First, don't heave it in the dump. Second, never a good idea to fire up an amp that's been in storage for decades, especially a tube amp that runs on internal high voltage. Filter caps hate to be re-awakened with 400-500 volts after such a long sleep. The best thing to do is plug it into a Variac and slowly bring up the AC line voltage while monitoring the amp for overheating filter caps and excessive line current draw. Maybe you have the gear to do that. If you get it to the point where you can run it on a full 120 VAC with no trouble, you could plug the output of a CD player or Ipod into it instead of a guitar, for a signal source to prove it does amplify.

If it's just a matter of get rid of it, as-is, Craigslist works pretty well. Pass along the admonition about not just plugging it in and hope it works if the buyer doesn't already know. That's one way to make a smoke machine.

As-is, not known to be working, expect $50-75. Proven working, add a couple hundred. It may be worth the effort.

You might want to start a fresh thread for this, or put it in the "for sale" department here at TAG. If you decide to work on it yourself, no worries, you can get a lot of advice here.

[SkOrPn]

I found one of these Mitchell PRO 100's in the attic today. <snip> Can someone tell me if this would be worth cleaning up and selling on Craigslist or eBay please? Or is it worthless and I just take it to the dump? Since I am an electronics tech, is there something I can do with it to make it more valuable and worth selling? How can I test it without a guitar?

Rod

First, don't heave it in the dump. Second, never a good idea to fire up an amp that's been in storage for decades, especially a tube amp that runs on internal high voltage. Filter caps hate to be re-awakened with 400-500 volts after such a long sleep. The best thing to do is plug it into a Variac and slowly bring up the AC line voltage while monitoring the amp for overheating filter caps and excessive line current draw. Maybe you have the gear to do that. If you get it to the point where you can run it on a full 120 VAC with no trouble, you could plug the output of a CD player or Ipod into it instead of a guitar, for a signal source to prove it does amplify.

If it's just a matter of get rid of it, as-is, Craigslist works pretty well. Pass along the admonition about not just plugging it in and hope it works if the buyer doesn't already know. That's one way to make a smoke machine.

As-is, not known to be working, expect $50-75. Proven working, add a couple hundred. It may be worth the effort.

You might want to start a fresh thread for this, or put it in the "for sale" department here at TAG. If you decide to work on it yourself, no worries, you can get a lot of advice here.

Thank you very much for the reply. Yeah, I figured I better not even think about plugging it in, so I did not even try that. Besides, as heavy as it is I went a head and lugged it out of the attic after posting above. It is FILTHY from years of dust. The dust did not blow off very well so that means I have to clean it with a brush and vinyl cleaner. One tube is missing (has 4 tube sockets) and I can't remember why or if it just did not have one when I got it. I never used it, not once. Someone at Youtube said he paid 400 for his, but I have my doubts unless it was brand new. $50? I would be shocked if it was worth that much in its current state of looks. I'm going to sell the tubes, all three for $20 on ebay OR sell the entire thing on CL for $20. With three 6L6 tubes (ones missing for some reason) it should be worth $20 I think, assuming the tubes didn't go bad after all these years sitting. I want to say the guy I got it from said it only needed a tube to get it functional, but being that its been 17 years since the conversation took place my brain can make up any story it wants, hahaha.

By the way, can you explain why it has two inputs and two outputs when the ones I see online have only one input? Is this for one guitar speaker and one microphone speaker for a singer? If so, I understand now why I took this in place of cash as it may have been a good starter amp. I used to build speaker boxes and professional car audio installations (1980's on and off work) so I have a feeling I was intending to "try" and build my own speakers for it.

Anyway, thanks for entertaining me with the ideas. I'm going to say its not worth anything (judging by its cover), maybe vacuum tube value at most, so I am going to put it on CL and hope the wife does not throw it out before someone comes and gets it. Thank again and take care Leo...

[Leo_Gnardo]

The dust did not blow off very well so that means I have to clean it with a brush and vinyl cleaner. One tube is missing (has 4 tube sockets) and I can't remember why or if it just did not have one when I got it. I never used it, not once. Someone at Youtube said he paid 400 for his, but I have my doubts unless it was brand new. $50? I would be shocked if it was worth that much in its current state of looks. I'm going to sell the tubes, all three for $20 on ebay OR sell the entire thing on CL for $20. With three 6L6 tubes (ones missing for some reason) it should be worth $20 I think, assuming the tubes didn't go bad after all these years sitting. I want to say the guy I got it from said it only needed a tube to get it functional, but being that its been 17 years since the conversation took place my brain can make up any story it wants, hahaha.

By the way, can you explain why it has two inputs and two outputs when the ones I see online have only one input? Is this for one guitar speaker and one microphone speaker for a singer? If so, I understand now why I took this in place of cash as it may have been a good starter amp. I used to build speaker boxes and professional car audio installations (1980's on and off work) so I have a feeling I was intending to "try" and build my own speakers for it.

Anyway, thanks for entertaining me with the ideas. I'm going to say its not worth anything (judging by its cover), maybe vacuum tube value at most, so I am going to put it on CL and hope the wife does not throw it out before someone comes and gets it. Thank again and take care Leo...

If you're going to let it go at $20, somebody's going to regard that as a huge bargain, dust and all, so don't bother cleaning up. It should be gone before you have time to think about it.

OTOH if you do go about it, no vinyl cleaner needed. A little dish detergent in warm water, a castaway toothbrush or fingernail brush, an old disposable towel, and half an hour's elbow grease should do just fine.

Tubes don't go bad all by themselves in storage. Although there are some wags who spread goofy stories that they do - hogwash.

Not very familiar with Mitchells particularly, but on any amp 2 inputs with only one set of controls usually means one of the inputs is full strength, and the second is padded down a bit, meant for accepting higher level signals (from pedal overdrives/fuzz boxes and/or guitars with built in preamps or active pickups like EMG), and gives from 6 to 20 dB less gain. Outputs, a main speaker and an extension is what we usually see.

With one output tube missing, the amp will function all right for a test. There will be uneven current drawn on each side of the output transformer primary, and that will likely result in a bit of hum, but that's no worry. When a full set of matched tubes is installed, likely the amp will turn out a clean 70 to 100 watts and that hum from imbalance will be gone. Likely will have scratchy controls too but a shot of quality cleaner to each one should bring them around. A lot of people use Caig D-5 and that's what I recommend. It only takes a little, hosing down the pots thinking more is better, that doesn't work. Even if you don't go about fixing it, you may want to pass along whatever you've gathered here on to the buyer in case they're not hip to reviving old amps properly.

You could list it here & maybe one of our New Mexico correspondents would grab it in a flash at $20, that would be a treat for them.

[tele_player]

[nevermind]

[eniam rognab]

shit, ill pay $20 and shipping to sacramento, assuming its just a head....

[SkOrPn]

I would prefer to post some good pics first before considering it worth anything. Its HEAVY and does not look all that great, to me anyway. Must be expensive to ship as well, wow.

Anyway, I will find the for sale thread and post some pics and maybe see if I get offers, lol... Just looking at the Manufactured in California blew me away HAHA. Really an American made electronic device??? I thought that became extinct by the 1980's, lol...

Thanks again guys.

[xtian]

I would also be interested in buying it. So I guess Neal and I will have to cage match.