JCM800 2203X reissue- No sound when effects loop is engaged

rock4ever

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I'm trying to help someone who I just sold an amp to, so it's on the other side of the USA and not with me.

He states the amp works great, but no sound when the effects loop is engaged. He's played with the 2 buttons near the loop return input. He also put a patch cable in the loop and still no sound

Any idea what might cause this?

Amp was produced in 2003, I am the 3rd owner. Looking at the outside of the amp everything- caps/ot etc looked stock.
 

South Park

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Try plugging your guitar into the send and return jack .
 

william vogel

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Did you test it and it worked properly right before you boxed it up and shipped it?
 

william vogel

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Regretfully, the amp was tested prior to listing sometime over the summer and sat unused in the interim.
Most likely it worked before shipping but because it wasn’t confirmed, we’re kind of at a loss. Shipping is the roughest thing I’ve ever found to be done with an amp. It gets dropped and if it’s not isolated very well, it’ll be damaged. The damage is usually not visible unless they really tossed it about.
 

jsessions

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Hey, new owner of the JCM 800 in question here. I reseated the preamp tubes and started to get a really subtle quick gated sound when plugging into the return. I noticed one of the preamp tubes was pretty dimly lit so I replaced it but unfortunately this didn't help. rock4ever went above and beyond with packaging the head for shipping(took me 15 minutes to get that thing out of all the packaging) but I wouldn't be surprised if something still happened in shipping. Maybe a loose connection or one of the jacks just needs to be replaced? Still waiting to hear back from a local amp repair guy to see if he thinks he can take a look at it.

Aside from this unfortunate FX loop issue, I absolutely love this amp. This is my first real Marshall (10" MG practice amp doesn't count right?) and I'm understanding what all the fuss is about. Hopefully, I can get this figured out soon, I appreciate @rock4ever for doing his best to help me out with this. I know sometimes things just happen that are out of your control and there is always a roll of the dice with shipping amps across the country.
 

paul-e-mann

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Hey, new owner of the JCM 800 in question here. I reseated the preamp tubes and started to get a really subtle quick gated sound when plugging into the return. I noticed one of the preamp tubes was pretty dimly lit so I replaced it but unfortunately this didn't help. rock4ever went above and beyond with packaging the head for shipping(took me 15 minutes to get that thing out of all the packaging) but I wouldn't be surprised if something still happened in shipping. Maybe a loose connection or one of the jacks just needs to be replaced? Still waiting to hear back from a local amp repair guy to see if he thinks he can take a look at it.

Aside from this unfortunate FX loop issue, I absolutely love this amp. This is my first real Marshall (10" MG practice amp doesn't count right?) and I'm understanding what all the fuss is about. Hopefully, I can get this figured out soon, I appreciate @rock4ever for doing his best to help me out with this. I know sometimes things just happen that are out of your control and there is always a roll of the dice with shipping amps across the country.
Congrats on the new amp and welcome to the forum! I wouldnt worry about it I suspect it will be something simple like a bad solder joint or jack. :yesway:
 

jsessions

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Congrats on the new amp and welcome to the forum! I wouldnt worry about it I suspect it will be something simple like a bad solder joint or jack. :yesway:
Thanks! Dropped it off at a tech earlier today so we'll see what he says. Honestly, I heard the FX loop was kind of bad on the X series even when it is functioning properly, so depending on the severity of the current problem I might end up putting a different one in anyways.
 

william vogel

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Thanks! Dropped it off at a tech earlier today so we'll see what he says. Honestly, I heard the FX loop was kind of bad on the X series even when it is functioning properly, so depending on the severity of the current problem I might end up putting a different one in anyways.
How loud is that amp? I’ve been around plenty of 100 watt Plexi’s but not a 2203. I just finished building a 40 watt version of a 2204 and it’s magically loud for it’s wattage, I can’t imagine a 100 watt version in my shop. You can check it out in the Building The Classics forum.
 

jsessions

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How loud is that amp? I’ve been around plenty of 100 watt Plexi’s but not a 2203. I just finished building a 40 watt version of a 2204 and it’s magically loud for it’s wattage, I can’t imagine a 100 watt version in my shop. You can check it out in the Building The Classics forum.
Oh cool I'll have to check it out! I've been building a lot of pedals the past few months and I'm definitely interested in building an amp now that I have a halfway decent understanding of analog electronics, at least in the scope of guitar equipment.

Yeah, there is definitely something magically loud about my JCM too. I've had 100+ watt tube heads and combos in the past, but nothing has compared to the way this thing shook me when I turned it on for the first time. Honestly, I couldn't turn the master past 2-3 unattenuated without shaking the house. Definitely going to turn that thing up when I eventually get it back and I wouldn't be surprised if the police arrive shortly afterward. Might as well try and even out the tinnitus in the other ear right?
 

rock4ever

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I cranked it in a 15x15 spare bedroom I have, door closed, with ear protection. I was not used to that kind of environment and I can only describe it as somewhat frightening. My entire body just shook from vibrations caused by that much air moving. My cab is a 1936cab, I imagine a 4x12 would be even more startling.
 

wernersaurus

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FX Loop is on a separate little circuit board - may have taken the chip out or the circuit that delivers the +30VDC is broken. That +30VDC is taken from the valve supply via a 47k/10W resistor and then artificially made a +-15VDC - pretty crude !
 

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OrangeDrop

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I have the same amp and the FX loop is very noisy! Luckily I don't use it and have it bypassed as it should be!
 
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OrangeDrop

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How loud is that amp? I’ve been around plenty of 100 watt Plexi’s but not a 2203. I just finished building a 40 watt version of a 2204 and it’s magically loud for it’s wattage, I can’t imagine a 100 watt version in my shop. You can check it out in the Building The Classics forum.
Very!
 

jsessions

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Got it repaired. There was a giant 10w 47k resistor that was blown and had to be replaced. I would love to mod this loop though because I really dislike the way that comes after the master.
 

Crikey

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Hey, new owner of the JCM 800 in question here. I reseated the preamp tubes and started to get a really subtle quick gated sound when plugging into the return. I noticed one of the preamp tubes was pretty dimly lit so I replaced it but unfortunately this didn't help. rock4ever went above and beyond with packaging the head for shipping(took me 15 minutes to get that thing out of all the packaging) but I wouldn't be surprised if something still happened in shipping. Maybe a loose connection or one of the jacks just needs to be replaced? Still waiting to hear back from a local amp repair guy to see if he thinks he can take a look at it.

Aside from this unfortunate FX loop issue, I absolutely love this amp. This is my first real Marshall (10" MG practice amp doesn't count right?) and I'm understanding what all the fuss is about. Hopefully, I can get this figured out soon, I appreciate @rock4ever for doing his best to help me out with this. I know sometimes things just happen that are out of your control and there is always a roll of the dice with shipping amps across the country.[/QUOTE
 

Crikey

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Got it repaired. There was a giant 10w 47k resistor that was blown and had to be replaced. I would love to mod this loop though because I really dislike the way that comes after the master.
Congrats
Enjoy
 


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