Help! My '77 Music Man 210 HD 130 shorted out from overheating.

[Casey Jones]

Hi,

I have a '77-ish Music Man HD 130 210 combo amp, that I've been using for home use only for a year or two with no issues except for the reverb which seems to only fully work whenever it feels I've provided the right amount mojo to her. :knockedou

For the last two months I've been using it as a bass amp for my band, and she has done wonderfully set on the first channel/ 65watts/ with the EQs set at an average of 7 across the board. The sound was spot on and I didn't feel like I was pushing it too hard, though it did feel hot after a couple of hours of practice. I should have already set up a fan behind it at this point or something to prevent such an event. :bigeyes::duh::duh:

Well yesterday I thought I'd flip the switch up to 130watts, the sound was pure heaven, and I wasn't expecting it, but I fried something after less than an hour. :guilty: After inspecting the issue, I saw smoke coming from the far left tube, my amp doesn't have the 12ax7 tube, but do have the 4 original 6 CA7's which I hope are okay after this.

I feel stupid as hell, I just had to flip that switch!! :crazy:

So I'm wondering if there are any straight forward plans, instructions, or resources to fix this issue myself. I do know how to use a soldering iron and do guitar wiring / etc, so I figured I should start to learn how to repair amps now that my amp needs to be fixed.

Any tools, frequency readers (is that a thing?, the sign wave deally), precautions, deals on parts, where to get them, how to test them, pictures... I know I'm asking a lot but money is tight and I'd rather spend it on a 115 extension cab to round out my original sound instead of getting a whole new rig, (which we are trying to do before our next practice in two days!).

Just want to say thanks in advance to all the amp wizards out there that can help me go in the right direction with this.

 

[Casey Jones]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

 

[zenmindbeginner]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Probably needs a new output transformer if it started smoking. Any Fender repair guy should be able to fix it as long as you provide the proper schematics.

On a side note... the pilot LED on my 1966 Princeton went out last night. : (

 

[Casey Jones]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Sorry about your 1966 Princeton, I love my amp and I was devastated when this happened.

Any idea on a reasonable price for the labor and part for that job? Is it something I could do easily without going to a tech?

Buy the correct transformer and replace from the old one seems pretty straight forward to me, I've just never taken apart a chasis before but have seen it done.

 

[zenmindbeginner]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Sorry about your 1966 Princeton, I love my amp and I was devastated when this happened.

Any idea on a reasonable price for the labor and part for that job? Is it something I could do easily without going to a tech?

Buy the correct transformer and replace from the old one seems pretty straight forward to me, I've just never taken apart a chasis before but have seen it done.

Well... $40 an hour is a reasonable rate. You can probably get a free or low cost estimate. The better repair guys will allow you to apply your estimate fee towards the repair bill.

The larger the city you live in... the more repairmen you'll have to choose from.

Where I live in Western/Central NC... there are TWO guys I can go to that are within an hour's drive from me. One guy won't return my calls and the other has fixed stuff before and I wasn't totally happy with his work.

Hopefully you live in a decent market with lots of musicians. If I lived in the East of NC, I'd have several talented guys to choose from but that's out of my driving range.

I don't think you'll be able to diagnose a bad transformer effectively without an oscilloscope but you can check for infinite resistance with a multimeter and that's sort of a start.

 

[Casey Jones]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Well... $40 an hour is a reasonable rate. You can probably get a free or low cost estimate. The better repair guys will allow you to apply your estimate fee towards the repair bill.

The larger the city you live in... the more repairmen you'll have to choose from.

Where I live in Western/Central NC... there are TWO guys I can go to that are within an hour's drive from me. One guy won't return my calls and the other has fixed stuff before and I wasn't totally happy with his work.

Hopefully you live in a decent market with lots of musicians. If I lived in the East of NC, I'd have several talented guys to choose from but that's out of my driving range.

I don't think you'll be able to diagnose a bad transformer effectively without an oscilloscope but you can check for infinite resistance with a multimeter and that's sort of a start.

Well I live in LA which is a double edged sword, a lot of techs but that also means more competition and higher labor costs. I found a guy about an hour away that said labor would be $45, but said that he wouldn't accept parts that I brought him because he couldn't guarantee his work. Fair enough, but then said that he marks up the prices on parts/ shipping / that he ordered himself... So I don't know, I might be better off buying the transformer, the oscilloscope, and the thing that biases tubes and have the capabilities to fix amps because I have two other bass amps that are fried and need repairs as well. An Acoustic B10 I got in a bad trade (it was fried and I didn't test it), and a Carvin BX 500 a friend gave me after he fried it.

I just hope my band mate and I can find a replacement in a day or two for practice until I figure this out.

Can you tell me if these prices for a replacement transformer are reasonable?? I just read that the transformer is most expensive part in the amp, great.

http://www.mercurymagnetics.com/pages/catalog/manufacturers/MM_musicman.htm

Thanks.

 

[GoldenVulture]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

I wouldn't presume it's the transformer, plenty of things cause smoke, such as resistors when they die. It could easily be one associatted with your output valves. I would inspect it [ unplug and remove the chassis from the cabinet ] Fried resistors can be visually obvious. Do you have/know how to use a multimeter ? If you open it up , take pics and post them here. Also take out your output valves and put them some where safe before removing the chassis.

So I'm wondering if there are any straight forward plans, instructions, or resources to fix this issue myself. I do know how to use a soldering iron and do guitar wiring / etc, so I figured I should start to learn how to repair amps now that my amp needs to be fixed.

Any tools, frequency readers (is that a thing?, the sign wave deally), precautions, deals on parts, where to get them, how to test them, pictures..

 

[zzmoore]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

I wouldn't presume it's the transformer, plenty of things cause smoke, such as resistors when they die. It could easily be one associatted with your output valves. I would inspect it [ unplug and remove the chassis from the cabinet ] Fried resistors can be visually obvious. Do you have/know how to use a multimeter ? If you open it up , take pics and post them here.

Yeah...I would start with this. ^^^^^^^
A good chance you had a power tube fail, and it took out a screen resistor.
That will make quite an odor.
You will just have to pull the chassis and take a look.
Per usual.....Drain/Check the caps before you start grabbing hold of anything.
best

 

[zenmindbeginner]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Well I live in LA which is a double edged sword, a lot of techs but that also means more competition and higher labor costs. I found a guy about an hour away that said labor would be $45, but said that he wouldn't accept parts that I brought him because he couldn't guarantee his work. Fair enough, but then said that he marks up the prices on parts/ shipping / that he ordered himself... So I don't know, I might be better off buying the transformer, the oscilloscope, and the thing that biases tubes and have the capabilities to fix amps because I have two other bass amps that are fried and need repairs as well. An Acoustic B10 I got in a bad trade (it was fried and I didn't test it), and a Carvin BX 500 a friend gave me after he fried it.

I just hope my band mate and I can find a replacement in a day or two for practice until I figure this out.

Can you tell me if these prices for a replacement transformer are reasonable?? I just read that the transformer is most expensive part in the amp, great.

http://www.mercurymagnetics.com/pages/catalog/manufacturers/MM_musicman.htm

Thanks.

Yeah, I wouldn't buy any parts until you find out which one failed... I don't see why you wouldn't just take it to a good tech so they can run some diagnostics.

If you've never discharged caps before... I suggest you just send it to a tech.

All techs mark up their parts a bit, it won't amount to too much... the parts cost could theoretically be very low depending on what failed.

Plus, developing a relationship with a good tech is really important since not all repairs are easily self serviceable.

You could theoretically get seriously hurt if the cap discharge doesn't go properly... just that fact alone sends my vintage tube amps to a tech.

That amp you have is good enough to warrant a visit to the doctor... no need for self surgery.

 

[Casey Jones]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Yeah...I would start with this. ^^^^^^^
A good chance you had a power tube fail, and it took out a screen resistor.
That will make quite an odor.
You will just have to pull the chassis and take a look.
Per usual.....Drain/Check the caps before you start grabbing hold of anything.
best

Hey thanks guys,

I will attempt this in the next few days and post my results with pics. I do have a multimeter but not sure that it can read caps and resistors, I will pick one of those up as well. I have two questions in the mean time..

How do I drain the caps and resistors?

And which way does the electricity flow? From Transformer to tubes to the rest of the internal components?

And Yes there was quite a smell in the studio from this.

 

[zzmoore]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Well.....first pull the chassis and take some clear pics.
Youtube will explain Cap Discharge. You should watch a few.

If you buy a 1k-100k 5 watt resistor and a pair of test leads, you can make a drain.
Radios Shack sells leads for cheap.
In a pinch you can just ground them straight to the chassis. The ground lug of the power cord usually is an easy discharge tool...you can use a pair of needle noise pliers to bridge to ground...or if you can get to the cap, a screwdriver.
But TRY to do it the right way your fist time.


Set your DMM to VDC. Clip one probe to chassis ground and then probe (pin 3 and 4 I believe...just check them all.) all the pins of one of your power tubes.
Use the drain to discharge the pins with High VDC. One tube should get all the caps...but check them all just to be safe.
As long as you do not see anything more than 10 VDC you are fine.


After you are clear of High Voltage, you can (assuming they are burned...who knows what will look bad in there) measure the resistance of (for example) the screen resistors on Pin 4. Just set your meter to Ohms/Resistance and put a probe on each side of the resistor. You are probably looking for a 1k5 resistor...probably 5 watts or bigger. But again...you need to open the chassis first, and see what you see.
good luck
FWIW ...In a nutshell...electron path of travel is ...PT, ground, (-)caps/power supply, cathode of tubes, plates of tubes, OT, (+)caps/power supply, rectifier, back to the PT.

 

[Edgecrusher]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

How do I drain the caps and resistors?

Dont... If you dont know what your doing dont mess with this. Until you are sure you know how to drain caps without asking on the net dont attempt it. Learn what the multi meter does dont even think about touching that amp. Save yourself the heart ache and take it to a tech.

 

[Gearjoneser]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

My first thought was a screen resistor, especially since the amp has probably never had any maintenance. I'm not sure if the amp has a bias mini pot or not, and assume the tubes were running hot.

I'd open it up like ZZMoore said and look at the tube sockets. You'll probably see a burned resistor and a burn mark on the socket. Whether you pay someone to fix it or try to fix it yourself, buy a full set of power tubes first. This way, you're getting them at a cheap price, not an inflated price the tech may charge. You need them anyway.

I'd suggest having a tech fix the problem, change the filter caps since it's due, and hand him your tubes to install. Then, you'll only pay labor and a small amount for the components.

 

[FretFire]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Take it to a tech.

Seriously, take it to a tech.

If you get the urge to buy parts, take it to a tech.

 

[karpathion]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

As someone who has knocked himself across the room by playing with things that he shouldn't, listen to these guys. Take it to a tech! You can kill yourself in there.

After damn near killing myself, I took a 2 year course on Electronics Technologies, and I still handle tube amps with extreme caution. There are some scary voltages in there, even when it's powered off.

This is for your safety.

 

[BrianS.]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

Dont... If you dont know what your doing dont mess with this. Until you are sure you know how to drain caps without asking on the net dont attempt it. Learn what the multi meter does dont even think about touching that amp. Save yourself the heart ache and take it to a tech.

Please.

 

[Gearjoneser]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

As someone who has knocked himself across the room by playing with things that he shouldn't, listen to these guys. Take it to a tech! You can kill yourself in there.

After damn near killing myself, I took a 2 year course on Electronics Technologies, and I still handle tube amps with extreme caution. There are some scary voltages in there, even when it's powered off.

This is for your safety.

I have an Electronic Technician certification, and can't tell you how many times I've fried my own azz, burned fingers, jump started my heart, and dropped amps on the floor. One hand with a plastic handled screwdriver, and one hand behind my back is something I learned the hard way! LOL

 

[guitfiddle]

Re: Help! My '77 Music Man 210 HD 130 shorted out from overheating.

When you take it to the tech with new tubes, remember to make him give you the old tubes or else leave them at home...they might not be anything super special, but they'll be US made tubes at any rate.

+1 for not trying to repair it yourself. Those amps put around 700 volts on the tubes when they're running.