200 volt B+ drop!?

[navdave]

Well I got an Egnater TOL up and running that was damaged in transit for a customer. Flipped it on to play it and was greeted with pretty loud buzz also when playing the amp notes and cords sound like there's a tremolo or vibrato effect going on. The other thing happening is when the amps on standby the b+ voltage is 553vdc when on the voltage drops to 358vdc yikes! He has two of these amps and the other runs at about 490vdc under load. Part of the shipping damage was the toroidal power transformer broke loose
tearing off a small patch of the plastic casing. Some of outer wire is exposed and I believe some of the
enamel on the wire came off could this be the problem?

[kagliostro]

A voltage drop may be due to a filter cap trouble


give a look and try if is that the reason on that amp


K

[navdave]

Part of the repair included all new filter caps. On standby the two b+ filter caps are charged and read 553v.
As soon as I flip it on there's that huge power drain. Could a new cap down stream be bad?

A voltage drop may be due to a filter cap trouble


give a look and try if is that the reason on that amp


K

[stratele52]

Remove all tubes an see what happened . Output tubes short ? Or too much current load ?

[navdave]

ok did this....
no tubes:
standby off 558vdc
standby on at first drops to 450 then went up to 495 stayed there.
just for giggles I plugged in just one tube the phase inverter b+ went down to 472vdc?

Remove all tubes an see what happened . Output tubes short ? Or too much current load ?

[stratele52]

ok did this....
no tubes:
standby off 558vdc
standby on at first drops to 450 then went up to 495 stayed there.
just for giggles I plugged in just one tube the phase inverter b+ went down to 472vdc?

Remove all tubes an see what happened . Output tubes short ? Or too much current load ?

IMO there is a problem in power supply , rectifier or Power Transformer defective or broken solder ........


takes voltage reading close to the Power Transformer , somewhere you may see no voltage drop . defective parts between these 2 test points , where voltage drop and where voltage stay high


Any link for schematic ?

[eleventeen]

"I believe some of the enamel on the wire came off could this be the problem?"

Could be. Could be that the HV winding is good and the bias winding (or the bias pot) got lunched and the output tubes, when installed, are not getting sufficient negative bias and are thus in overcurrent. Assuming a transformer replacement is the least desirable outcome...you'd want to check for presence of adequate bias. (looking at the 100 watt version) check for something like -60 DC volts on the anode [non-bar end] of D7. Check also to see if you have -50 volts +/- on the pin 5's of the EL34s.

[navdave]

If I remember right the only voltage dropping is the main high voltage winding the bias and heater windings are holding steady at work now I'll have to check again tonight.

ok did this....
no tubes:
standby off 558vdc
standby on at first drops to 450 then went up to 495 stayed there.
just for giggles I plugged in just one tube the phase inverter b+ went down to 472vdc?

Remove all tubes an see what happened . Output tubes short ? Or too much current load ?

IMO there is a problem in power supply , rectifier or Power Transformer defective or broken solder ........


takes voltage reading close to the Power Transformer , somewhere you may see no voltage drop . defective parts between these 2 test points , where voltage drop and where voltage stay high


Any link for schematic ?

[navdave]

There's three other windings bias, power tube a/c heaters, and preamp tube d/c heater supply. I'll check again tonight but as far as I know there all doing fine.

"I believe some of the enamel on the wire came off could this be the problem?"

Could be. Could be that the HV winding is good and the bias winding (or the bias pot) got lunched and the output tubes, when installed, are not getting sufficient negative bias and are thus in overcurrent. Assuming a transformer replacement is the least desirable outcome...you'd want to check for presence of adequate bias. (looking at the 100 watt version) check for something like -60 DC volts on the anode [non-bar end] of D7. Check also to see if you have -50 volts +/- on the pin 5's of the EL34s.

[HotBluePlates]

... when the amps on standby the b+ voltage is 553vdc when on the voltage drops to 358vdc yikes! He has two of these amps and the other runs at about 490vdc under load. ...

Then the B+ doesn't drop 200v, it is dropping 132v (compared to the known good amp). You also expect the B+ to be high in standby, because the tubes draw no current from the B+ (same for every other amp in standby).

If you can install all preamp/phase inverter tubes and get a voltage nominally near 490vdc, then you have strong evidence the problem is with the output tubes and/or bias.

[stratele52]

... when the amps on standby the b+ voltage is 553vdc when on the voltage drops to 358vdc yikes! He has two of these amps and the other runs at about 490vdc under load. ...

Then the B+ doesn't drop 200v, it is dropping 132v (compared to the known good amp). You also expect the B+ to be high in standby, because the tubes draw no current from the B+ (same for every other amp in standby).

If you can install all preamp/phase inverter tubes and get a voltage nominally near 490vdc, then you have strong evidence the problem is with the output tubes and/or bias.

+1


1-  Put all 12XX7 tubes ; volt reading 


2- Put Output tube ; volts reading


3- Output  tube could be short


Or if any load draw too much current because Power Supply is weak ?

[navdave]

Does the same huge voltage drop with 6l6's and el34's the other problem is a loud buzz and the vibrato tremolo oscillation while playing the amp.

... when the amps on standby the b+ voltage is 553vdc when on the voltage drops to 358vdc yikes! He has two of these amps and the other runs at about 490vdc under load. ...

Then the B+ doesn't drop 200v, it is dropping 132v (compared to the known good amp). You also expect the B+ to be high in standby, because the tubes draw no current from the B+ (same for every other amp in standby).

If you can install all preamp/phase inverter tubes and get a voltage nominally near 490vdc, then you have strong evidence the problem is with the output tubes and/or bias.

[HotBluePlates]

Does it happen with all tubes in place except the output tubes? That's what I wanted to find out.

[stratele52]

Does it happen with all tubes in place except the output tubes? That's what I wanted to find out.

+1

[stratele52]

Does the same huge voltage drop with 6l6's and el34's the other problem is a loud buzz and the vibrato tremolo oscillation while playing the amp.

 

Loud Buzz , did you look at your output tubes while you play ?  Did Output tubes are good ?


Any link for schematic ?

[navdave]

Yeah it drops even when there's no tubes in the amp. Even puting one 12ax7 in made it drop.

Does it happen with all tubes in place except the output tubes? That's what I wanted to find out.

[navdave]

The schematic floating around on the web is for the Rocktron version of the TOL. This is an early 90's original version.

Does the same huge voltage drop with 6l6's and el34's the other problem is a loud buzz and the vibrato tremolo oscillation while playing the amp.

 

Loud Buzz , did you look at your output tubes while you play ?  Did Output tubes are good ?


Any link for schematic ?

[stratele52]

Yeah it drops even when there's no tubes in the amp. Even puting one 12ax7 in made it drop.

Power supply weak .

[navdave]

I have spare power transformer the main high voltage is 400v close to the Egnaters 380. I'm thinking of just wiring in the high voltage portion to see what results I get.

[stratele52]

I have spare power transformer the main high voltage is 400v close to the Egnaters 380. I'm thinking of just wiring in the high voltage portion to see what results I get.

Find where is a trouble BEFORE put any new part, easy if you follow trouble shouting step by step method .


AC volts reading at Power Transformer secondary ;


1-Volt drop or not ? If drop it is the Power T or wiring at primary or secondary, solder, printed circuit  ....
2- No voltage drop , check voltage at rectifier output , solder , etc ;
3- Voltage drop ; check rectifier , solder etc
4- Votage do not drop ; test volt reading after next part.........


And you'll find where is the trouble .

[stratele52]

The schematic floating around on the web is for the Rocktron version of the TOL. This is an early 90's original version.

 

Why Rocktron if you need TOL ?


I four few TOL on web , TOL 50 watts . TOL 100 watts. Wich one do you have ?


http://schems.com/manu/egnater/egnator_tol50_50w.pdf

[navdave]

Never thought of checking the high-voltage secondary so I did both on standby and off standby the AC voltage is steady at 408. On standby the two main filter caps are charged and hold the voltage until I turned the standby on
whenever the other side of that switch hits the choke and the rest of the filter caps that's when it looses B+ drastically. The big bummer is that all these filter caps are new and I don't own an ESR meter.

I have spare power transformer the main high voltage is 400v close to the Egnaters 380. I'm thinking of just wiring in the high voltage portion to see what results I get.

Find where is a trouble BEFORE put any new part, easy if you follow trouble shouting step by step method .


AC volts reading at Power Transformer secondary ;


1-Volt drop or not ? If drop it is the Power T or wiring at primary or secondary, solder, printed circuit  ....
2- No voltage drop , check voltage at rectifier output , solder , etc ;
3- Voltage drop ; check rectifier , solder etc
4- Votage do not drop ; test volt reading after next part.........


And you'll find where is the trouble .

[stratele52]

Ac is good = Power transformer is good


Check rectifier diodes


If  good , You may have a short somewhere on B+


Disconnect one by one each of B+ supply ( your arrows on the sketch from filter caps to circuits ) and see what happened .


Your B+ voltage must stay high when you'll disconect the shorted  B+ line. Then you trouble is in this circuit wich receive this B+

[navdave]

Thanks you to everyone ended up being the brand new main filter caps that were bad this was a first for me.
Cheers!

[stratele52]

Congrats !

[Ed_Chambley]

Thanks you to everyone ended up being the brand new main filter caps that were bad this was a first for me.
Cheers!

Where did you get them?  What is the date on them?  What brand?  Just want to avoid getting some of the same.  Thanks.

[navdave]

Mouser... I let them know and they sent me new ones free of charge no question asked and I didn't have to return the originals.

Thanks you to everyone ended up being the brand new main filter caps that were bad this was a first for me.
Cheers!

Where did you get them?  What is the date on them?  What brand?  Just want to avoid getting some of the same.  Thanks.

[kagliostro]

 

ended up being the brand new main filter caps that were bad

A voltage drop may be due to a filter cap trouble

give a look and try if is that the reason on that amp

Ahem ..... ............  .............. 



No ..................    I don' t have a crystal ball, but at a friend, long ago, happened the same thing ...........


Ciao

K 

[stratele52]

Navdave ,


Like Ed chambley ask , what brand  ?

[stratele52]

ended up being the brand new main filter caps that were bad

A voltage drop may be due to a filter cap trouble

give a look and try if is that the reason on that amp

Ahem ..... ............  .............. 



No ..................    I don' t have a crystal ball, but at a friend, long ago, happened the same thing ...........


Ciao

K

+1 Kagliostro