Weirdness w/Carvin X100b combo

[Rand-O-Monium]

Just wondering about a vague troubleshoot.The input is dead(no signal/LED),but I'm still able to use the Pwr Amp in to get signal to the spkr.Was using it to power my spare pre-amp for a kick-around rig,& it stayed on a lot.Seems if the amp was blown,I wouldn't get anything out of it,but the power tubes are lighting up,so I was able to use it like that.Still kinda sucks,tho I really liked the tone shaping that the controls offered,& the output is considerably reduced.
Any thoughts on the matter would be appreciated.I don't have the amp here,tho,so can't really be too specific regarding questions & I don't work on these kinda things.
Just some general hints would be helpful(if there are any),debating on whether it's worth fixing or not.Would be nice to have it up & running,but my Marshall combo's new switch is a higher priority.
Thanx for any help...

 

[Gearjoneser]

Re: Weirdness w/Carvin X100b combo

1. Clean out the FX loop jacks, and continuously plug a cable in and out of them.

2. Put a short guitar cable in the FX loop with no effect unit. Plug the guitar into the input.
See if signal gets from the preamp section to the power section.

3. Change all the preamp tubes.

4. Examine the connection between the input jack and the circuit board. Make sure the solder joint isn't cracked or something in this area isn't defective.

 

[Demanic]

Re: Weirdness w/Carvin X100b combo

If the led isn't lighting up, I would say that something has shorted out the entire pre-amp section.

 

[jackson111]

Re: Weirdness w/Carvin X100b combo

I also own a x100b and haven't had any problems, but I do know that carvin support is great to work with. I would call carvin and a lot of times they can guide you through simple troubleshooting that can narrow down the problem. one thing you can check is to make sure that all connections internal are properly seated and clean. I have never had to open my x100b but I do know that some of the carvin amps use ribbon cables to join the preamp section to the power section. I assume the x100b uses this setup as well, because you can order replacement boards for the effects loop, pre amp, reverb, and power section board. so if you ever do have a board go bad you only have to replace the board that has gone bad instead of the entire master board like you would for most amps where everything is on one board. even if the connections are tight I have heard of people having to clean them periodically. I hope this helps but seriously call carvin they will do their best to help you out without having to take it to a tech..

 

[Demanic]

Re: Weirdness w/Carvin X100b combo

I have an XV-212 from the mid 80's and I have opened it up to check for a bias pot (there is none on this model, though I have heard of a mod for one). I don't recall seeing such on mine, but as I said, it's an older model. That is a good thing to know about Carvin support though.

 

[sosomething]

Re: Weirdness w/Carvin X100b combo

If the led isn't lighting up, I would say that something has shorted out the entire pre-amp section.

Bingo.

 

[jtougas]

Re: Weirdness w/Carvin X100b combo

Fuse check?

 

[ehdwuld]

Re: Weirdness w/Carvin X100b combo

My first thought was along the lines of what Gearjonser said
then then input jack made sense
then the ribbon cable
then the Carvin Tech support

these sounded familiar because when I emailed Carvin tech support when I had trouble with my Belair
these are the same things the tech said

if the amp has been jarred badly, check the cable
bad input jack or effects loop wouldn't make the light not come on

say none of the preamp tubes light up ?

Ribbon Cable
most likely

 

[GilmourD]

Re: Weirdness w/Carvin X100b combo

If the led isn't lighting up, I would say that something has shorted out the entire pre-amp section.

LED's usually powered by the heaters, so I almost wonder if the heaters just aren't working at all. 12AX7s are going to be a bit more sensitive to that. The power tubes might be indirectly heating the cathode enough to function, but you're stripping the cathodes to death if the heaters are shot.

I wouldn't continue to use it as you have been just in case that is what happened.