__Triple Recto problems....?

[AXEnGEAR4J]

-First I would like to introduce myself and say hi as a "newbie" to this forum, been active in many other forums, mostly vintage amp. l enjoy Mesa engineering and quality, own a 2CH Triple, 3CH Dual and a Heartbreaker.-

Question: First experienced a loss of volume, started to fluxuate from good high then low then high, finally lost all volume. All power tubes except for one (far right) do not light up.
The rectifier tubes do not light up either however they do warm up and get hot like the heaters are working.

I swapped out tubes with no change, ideas ??

 

[ryjan]

Welcome aboard! Did you change the rectifier and preamp tubes as well? Try diode rectification? Sounds like a power tube failed and took a resistor with it.

 

[etrium]

what about preamp tubes? do they light up?

 

[AXEnGEAR4J]

Yes, preamp tubes light up fine
Only one power tube (far right) will light up
Heat in rectifier tubes but no glow

Still no go when on diode rectifier...

what about preamp tubes? do they light up?

 

[etrium]

as ryjan said try diodes rectification and see what happens

 

[AudioMonk]

Hello. Whether or not the heaters light on the output tubes has nothing to do with the rectifiers, tube or solid state. The 6.3v heater winding for the output tubes is completely independent of both the high voltage ac secondaries and the 5v winding for the rectifiers. What you need to do is remove all power tubes and put the amp on standby in solid state mode, just so you don't confuse yourself. Next, one by one, replace the output tubes into the socket that you know is lighting..again still in standby. What 15 seconds or so and watch and feel if tube lights and gets hot. Do this one tube at a time in the same socket all in standby mode. This will tell you if the tubes are shot or there is a problem with the heater winding on the transformer or something related. It's not common to have the filaments go down on this amp unless there was some weird short going on from foreign matter getting in the amp. And the filaments are wired in series...so if one goes down so will the rest.

 

[AXEnGEAR4J]

Tried the tubes in another amp and the light up fine.

..and there no difference in either "rectifier" mode

Hello. Whether or not the heaters light on the output tubes has nothing to do with the rectifiers, tube or solid state. The 6.3v heater winding for the output tubes is completely independent of both the high voltage ac secondaries and the 5v winding for the rectifiers. What you need to do is remove all power tubes and put the amp on standby in solid state mode, just so you don't confuse yourself. Next, one by one, replace the output tubes into the socket that you know is lighting..again still in standby. What 15 seconds or so and watch and feel if tube lights and gets hot. Do this one tube at a time in the same socket all in standby mode. This will tell you if the tubes are shot or there is a problem with the heater winding on the transformer or something related. It's not common to have the filaments go down on this amp unless there was some weird short going on from foreign matter getting in the amp. And the filaments are wired in series...so if one goes down so will the rest.

 

[AudioMonk]

Hey. Sounds like a problem on the filament supply. The triple uses a pc board to which the output tube sockets and filament supply are soldered, that's where the prob lay. Are you looking to fix it yourself? Anything beyond this point requires the amp to be opened and the filament supply to be tested.

 

[AXEnGEAR4J]

hmm...I'm pretty good with a soldering iron and know most of the "safety issues" with amp repair just need to know where/how to look/test/fix..

I see where it's not easy to some across a schematic for a triple recto ??

Hey. Sounds like a problem on the filament supply. The triple uses a pc board to which the output tube sockets and filament supply are soldered, that's where the prob lay. Are you looking to fix it yourself? Anything beyond this point requires the amp to be opened and the filament supply to be tested.

 

[shytfayse]

Audiomonk is on the right path. Mesa does not issue schematics for current production amps. You would need to take the chassis out of the cab. One quick check is to use a voltmeter, on AC setting, remove the power tubes from the sockets, turn the power on, leaving standby off, and check for 6.3 Volts on pins 2 and 7 of each power tube socket. Mesa likes to use a circuit board that all the power amp section plugs into. If one heater is lighting up then 6.3 volts is getting to the board which means your power transformer is O.K. - a very good thing. I suspect a bad trace or a bad solder joint between the power tube that is heating up and the ones that do not. Good Luck. - Pat.

 

[AudioMonk]

I have pictures on my AudioMonk facebook page that show me digging into the belly of the beast that is the triple rec. It even shows where the green 6.3v heater wires attach. Two boards need to be removed in order to properly test.

 

[AXEnGEAR4J]

Any "need to know's" on accessing and removing the pcb's? I hear Boogie's can be a bit of a challenge...

 

[AXEnGEAR4J]

Ok tested all tube sockets, unless my meter is off both pins 2&7 read at 5V's, and I understand it should be 6.3 ??

 

[etrium]

yes it should be 6,3VAC

 

[AXEnGEAR4J]

ok interesting situation....

Started to replace each tube one by one...turning the amp off/back on each time.
Every tube lit up until I got to the last tube...when I put that last one in the others went off and only the last one lit up??

 

[shytfayse]

Ensure that you are not reading the rectifier filament voltage which is 5 VAC between pins 2 and 8 on the 5U4 tubes. Are you reading the 5 volts AC with the power tubes in or out? Do the preamp tubes light up? V2 - V5 share the same 6.3V. Pull those too and make a measurement. V1's filament is 6 VDC where they rectify that same 6.3 VAC and perhaps one od these diodes are shorted pulling down the voltage to 5 VAC. Unplug the footswitch also to take a measurement as it uses the 6 VDC supply. With reguards to your last post, did you you slot the same tubes back into the same sockets from where they came? If you did, move the suspect tube that killed the other filaments from lighting to another socket to see if the problem moves or remains on the socket. After seeing your pics, your amp does not have a circuit board for the power tubes. The bare wire running on pins 2 and 7 that is closer to the chassis is the heater circuit. Inspect that for bad connections. - Pat.

 

[AXEnGEAR4J]

:shock:
tested all heater circuit; wires, pins, sockets, solder joints etc...

back to this.....I have taken the tubes out, back in and back out, (probably 6-7 times) all would light up until I put the last tube back in (closes to the source) and all would go out except for the one tube, same thing...then.....put different tubes back in and it worked! Then put the old tubes back in again, they all lit and worked!....

go figure... :roll: I was told this could happen...must have been the connections in the sockets...

Ensure that you are not reading the rectifier filament voltage which is 5 VAC between pins 2 and 8 on the 5U4 tubes. Are you reading the 5 volts AC with the power tubes in or out? Do the preamp tubes light up? V2 - V5 share the same 6.3V. Pull those too and make a measurement. V1's filament is 6 VDC where they rectify that same 6.3 VAC and perhaps one od these diodes are shorted pulling down the voltage to 5 VAC. Unplug the footswitch also to take a measurement as it uses the 6 VDC supply. With reguards to your last post, did you you slot the same tubes back into the same sockets from where they came? If you did, move the suspect tube that killed the other filaments from lighting to another socket to see if the problem moves or remains on the socket. After seeing your pics, your amp does not have a circuit board for the power tubes. The bare wire running on pins 2 and 7 that is closer to the chassis is the heater circuit. Inspect that for bad connections. - Pat.

 

[AudioMonk]

I'd change that first socket to make sure it doesn't go down when you least need it to.

 

[AXEnGEAR4J]

Okay I'm back to having the same problem when I notice the volume starting to fade again. Tried putting in different tubes and same thing. First powertube lights up and the rest don't. Heater wires and connections on all sockets are fine.
Back in the dark again...lol

:?:

 

[AXEnGEAR4J]

did a re-solder where the PT connects and the buss wires. Pin 7 did look questionable like possibly a cold joint when I put heat to it, much cleaner joint now and all tubes lighting up.