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I'm Afraid I've Done a Bad Thing.

forceof1

forceof1

Active Member
Ugh. Just got a Marantz 250. Worked great until I tried to run 2 right and left in series. Ohms are fine. Fired it up, came on for a split second and blew the fuse. I had 1 wire in the wrong place. From there I checked continuity to make sure all was good, another fuse. Disconnected all speaker wires, another fuse. What have I done :(
 
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Blowed up the amp, needing professional service, or if you can stop everything and show up here with the proper diagnostic tools, voltmeter with diode tester, soldering iron and knowledge to use it with proper solder, service manual and such, maybe someone will come along and hold your hand while you repair it yourself. This happens all the time. One guy didn't even know how to solder and got instructions here and on the web and got his unit up and running fully recapped and he is on a crusuade to save more gear from the bad sound of old caps.

If you don't want to follow directions and supply the request info, build a dim bulb tester (easy and cheap), a local AKer might step forward and offer some assistance or a repair as well as some shops in your area that might fix it for you.

don't put anymore fuses in it and try it, that can cause more damage.

Sorry for your loss.
 
I’m not that far from you, but I think the 250 is above my pay grade. I have not worked on one, and they have a reputation for being very particular about their setup when replacing outputs, etc. I would recommend looking for a trustworthy tech in your area - maybe Austin or San Antonio. And be prepared to spend some money. If you don’t find what you need locally, I can give you some recommendations for AK experts who can definitely fix it if you are willing to ship. Maybe give AK member Txturbo a PM. I believe he is in Austin. If he doesn’t work on them, he may know someone in your area that he trusts.
 
I can solder, have several meters, a schematic,
I need diagnostic tools (what type), and I'll find a service manual.

Approximation of professional fix?

THanks Blue Shadow, I really appreciate it.
 
Steven Tate said:
I’m not that far from you, but I think the 250 is above my pay grade. I have not worked on one, and they have a reputation for being very particular about their setup when replacing outputs, etc. I would recommend looking for a trustworthy tech in your area - maybe Austin or San Antonio. And be prepared to spend some money. If you don’t find what you need locally, I can definitely give you some recommendations for AK experts who can definitely fix it if you are willing to ship. Maybe give AK member Txturbo a PM. I believe he is in Austin. If he doesn’t work on them, he may know someone in your area that he trusts.
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Thank's for the local info. I only know one shop in Austin, been there forever. When you say "be prepared to spend some money, approximately how much is "some money? I'll give Txturbo a PM. Thanks!!
 
I’m not good at guessing tech costs, but I would think to trace down the problem and fix, maybe $300-400. Better yet, a complete restoration by a qualified person, maybe double that. Don’t hold me to that. It’s just a guess based on a few repair tabs I’ve seen.
Steve
 
forceof1 said:
Thank's for the local info. I only know one shop in Austin, been there forever. When you say "be prepared to spend some money, approximately how much is "some money? I'll give Txturbo a PM. Thanks!!
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DO !!!! get an estimate before any work is done. If some local tech is going to soak you then it would make more sense to have a professional (from this very posting group) do a full and PROPER!!!!! rebuild on your 250. The 250 is a classic and well worth having professional restored and upgraded. Then it will last you a lifetime.

The 250 is a twitchy thing to repair. They are stable and do work well. But once they break it's an entirely different beast to repair. Pro's (not familiar with the 250) have been unable to fix these.
 
Sorry for your loss, :mad:

Your handle is apropos forceof1. I feel your pain. I’m in Houston and have a dead 250 acquired recently. Will be rebuilding later this summer. Will be following your thread if decide to tackle on your own. Best
:lurk:
 
if you want to fix it yourself, i'd suggest getting a transistor checker (I got mine from Amazon), DBT, a watt meter, scope, function generator, and a couple volt meters. These amps eat transistors like popcorn.

There are a few threads here describing how to troubleshoot and fix. I have one but it was pretty much me posting what I was finding.
 
rickl said:
if you want to fix it yourself, i'd suggest getting a transistor checker , DBT, a watt meter, scope, function generator, and a couple volt meters. These amps eat transistors like popcorn..
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Don't forget to get match pairs of transistors. I believe (could be very wrong here) if they are not matched they will oscillate and blow. Also don't forget the driver transistors. Yeah, those as well. And while you're at it, recap the thing. and yes you will need at least two meters to set the amp adjustments.
 
airtime said:
DO !!!! get an estimate before any work is done. If some local tech is going to soak you then it would make more sense to have a professional (from this very posting group) do a full and PROPER!!!!! rebuild on your 250. The 250 is a classic and well worth having professional restored and upgraded. Then it will last you a lifetime.

The 250 is a twitchy thing to repair. They are stable and do work well. But once they break it's an entirely different beast to repair. Pro's (not familiar with the 250) have been unable to fix these.
Click to expand...

Thanks for the info, This amp was fully serviced before I got it. Hopefully this will make things a little less painful. Thank you for your help........
 
I
jd3rdcoast said:
Sorry for your loss, :mad:

Your handle is apropos forceof1. I feel your pain. I’m in Houston and have a dead 250 acquired recently. Will be rebuilding later this summer. Will be following your thread if decide to tackle on your own. Best
:lurk:
Click to expand...


'll be here. I'll review what others have done and decide if I have any business sticking my fingers in there!
 
Sorry to hear.

"Worked great until I tried to run 2 right and left in series. "
Does this mean you had the right channel in series with the left channel, or you had two speakers in series on each channel? If the latter that should have decreased the load on the amp, not increased it. I suppose that 'one wire in the wrong place' will explain it.

"Ohms are fine."
Does this mean the speakers still read the correct ohms so you know they are OK, or...?
 
toxcrusadr said:
Sorry to hear.

"Worked great until I tried to run 2 right and left in series. "
Does this mean you had the right channel in series with the left channel, or you had two speakers in series on each channel? If the latter that should have decreased the load on the amp, not increased it. I suppose that 'one wire in the wrong place' will explain it.

"Ohms are fine."
Does this mean the speakers still read the correct ohms so you know they are OK, or...?
Click to expand...


Well, I have 2 systems I wanted combine into 1. I used the already paired (regular spkr wire) as 1, say +. One wire I believe a - got placed on the + post. As far as Ohms, 16 ohms is within the spec
 
It does not matter if speakers are connected 'backwards' (plus to minus) since music is an AC type of signal. But, if you somehow connected the amp's + and - outputs together, i.e. a dead short, that could be bad. One would think the fuse would protect the output transistors but perhaps not.
 
forceof1 said:
Well, I have 2 systems I wanted combine into 1. I used the already paired (regular spkr wire) as 1, say +. One wire I believe a - got placed on the + post. As far as Ohms, 16 ohms is within the spec
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You didn't connect the + of one channel to the - on the other channel? That is a dead short.
 
I can tell you it took me about 10 years to get my 250 going. I'd have no problem today but the amp wasn't a priority when I first got it.

I still suggest you need to test every transistor on each amp board.
 
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