Jcm 800 2203 (no Sound) H.e.l.p.

[RyanScott]

All the tubes are lighting, the HT fuse is good, there is ZERO noise coming out of the amp, used different cabs and such. But I also noticed that although the tubes light, they are NOT SUPER HOT (before you couldn't touch them) without feeling some pain.

What should I be lookin for?

 

[GIBSON67]

Has anything changed from the last time it was working properly?

 

[tschrama]

No noise at all means no current through the output transformer. This is consistent with the tubes not getting really hot.

So either the HT has failed: check the HT

or the bias voltage has drop so low, that no current is flowing. : check bias current and grid voltage.

 

[ampmadscientist]

All the tubes are lighting, the HT fuse is good, there is ZERO noise coming out of the amp, used different cabs and such. But I also noticed that although the tubes light, they are NOT SUPER HOT (before you couldn't touch them) without feeling some pain.

What should I be lookin for?

Blown fuse caused by incorrect speaker load or bad speaker connections.

 

[RyanScott]

I'm not thinking so because I had correct setting on the amp matching the cab.

 

[RyanScott]

No noise at all means no current through the output transformer. This is consistent with the tubes not getting really hot.

So either the HT has failed: check the HT

or the bias voltage has drop so low, that no current is flowing. : check bias current and grid voltage.

Grid voltage test Im assuming on one of the Power Tube Pins?

 

[RyanScott]

Has anything changed from the last time it was working properly?

Nothing has changed, shut her down and she never woke up.

 

[tschrama]

Grid voltage test Im assuming on one of the Power Tube Pins?

Grid voltage test Im assuming on one of the Power Tube Pins?

If you have to ask about that, you should bring the amp go to a tech.

 

[ampmadscientist]

I'm not thinking so because I had correct setting on the amp matching the cab.

That doesn't mean that there is nothing wrong with the speaker or speaker connections. (like a bad jack or a bad speaker cable)

When the fuse blows it's usually speaker related. Remember this.
If the fuse blows - it blows for a reason.

Fuses don't blow by themselves - if the fuse blows, there IS something causing it to blow.

1. Don't ever assume that there could be nothing wrong. If the fuse blows check everything. Especially the speaker cables and jacks.

2. A bad connection inside a speaker plug can make the fuse blow.
3. A corroded jack in the speaker cabinet can make the fuse blow.

4. DID you measure the speaker with an ohm meter?

 

[RyanScott]

1. Speakers Cab and Cables work fine with my other JCM900

2. No fuses are blowing (not sure where you read that)

3. Speaker cab Ohm reading 15.7 (its a 16 ohm cabbie)

 

[RyanScott]

Heres a thought? Bad Standby Switch??

 

[johan.b]

2203 or 2203x? ..If x, put a cable in the loop
J

 

[neikeel]

Let's see:
Tubes lighting = mains fuse and heater circuit is working (probably ac HT out too, more later)
Did you check the HT fuse with a meter (not just by eye?).
Do the fx loop jumper first - quite common corrosion on the loop jack contacts.
Also give the output selector a good wiggle as they can make poor contact sometimes.
Next pull the amp from the chassis (usual rules of engagement re caps, although you should have bleeders on yours).
Plug in with output tubes removed (no need for speaker load then) and with DVM check for dc volts between chassis and the probe for B+ voltage from the rectifier 470-490 is ballpark, clip to chassis, one hand in pocket other on probe.
If that is good then measure plate voltage by moving probe to pin3 of each output tube, whilst there measure screen voltages (pin 4, smidge lower than plate) and for bias voltage on pin 5 (-ve volts of around 40 to 50v).
After that post back.

 

[neikeel]

Laggy net - double post!

 

[Rudy v]

All the tubes are lighting, the HT fuse is good, there is ZERO noise coming out of the amp, used different cabs and such. But I also noticed that although the tubes light, they are NOT SUPER HOT (before you couldn't touch them) without feeling some pain.

What should I be lookin for?

Have you thought a bad phase inverter tube

 

[Ufoscorpion]

Are you sure you've not just suddenly gone deaf from playing a 2203 too loud in your bedroom ?

 

[myersbw]

I conquer with pulling the power tubes and voltage checks first (including each side of the Standby switch). Yank the speaker cable from the amp and measure the resistance with a meter.

 

[ampmadscientist]

1. Speakers Cab and Cables work fine with my other JCM900

2. No fuses are blowing (not sure where you read that)

3. Speaker cab Ohm reading 15.7 (its a 16 ohm cabbie)

Take the power tubes out.
Turn power on, turn standby to operate.
Set DC voltmeter to highest range (usually 600 or 1000 volts)
Measure pin 3 and pin 4 of each output tube socket. Red probe to pin(s), black probe to chassis ground.
What is the readings?

 

[johan.b]

No posts since Oct.9...I think he solved it..
J

 

[ampmadscientist]

No posts since Oct.9...I think he solved it..
J

Well, he could have let us know...how gosh.