B-52 AT-100 Tri Mode Rectifier Explaination...

jammindude

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Hello, does anyone know what else i can do besides a fan in the back to draw the heat away from PT, that is what killed my last one, if anyone knows what changed from the AT100 to the ATX100 please let me know, or any simple mods to keep her running smooth, i installed a new reverb tank, now when i turn on reverb i get a loud hum, so i dont know what is happening, and is there any power tubes i can use that will not run as hot, I am learning, so no negative bs please, if i could afford a Bluesbreaker i would have one, Jan
 

Pete Farrington

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draw the heat away from PT, that is what killed my last one
I suggest that you should consider the potential / likely reasons why the PT was getting so hot as to become damaged. eg how much HT and heater (filament) current were the output valves drawing?
As you’re thinking, it would be extremely regrettable for a replacement PT to go the same way.
Were all the fuses the correct spec?
It’s a rather unusual PT, did you use an exact ‘like for like’ replacement?

installed a new reverb tank, now when i turn on reverb i get a loud hum
Have you got it oriented correctly, ie such that the reverb tank’s pick up transducer isn’t directly above the PT?

is there any power tubes i can use that will not run as hot
What output valves have you used, and how did you check that the bias was appropriate for them?

i could afford a Bluesbreaker i would have one
Compared to your current amp, that’s as different as chalk and cheese, or at least as much as any 2 valve guitar amps can be! Are you sure about aiming for such an extreme change?
 
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Chris-in-LA

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Hello, does anyone know what else i can do besides a fan in the back to draw the heat away from PT, that is what killed my last one, if anyone knows what changed from the AT100 to the ATX100 please let me know, or any simple mods to keep her running smooth, i installed a new reverb tank, now when i turn on reverb i get a loud hum, so i dont know what is happening, and is there any power tubes i can use that will not run as hot, I am learning, so no negative bs please, if i could afford a Bluesbreaker i would have one, Jan
You should send an email to Nik at Ceriatone and ask him about a Bluesbreaker kit as you seem to be asking about one in your profile. Their prices are reasonable.
 

jammindude

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You should send an email to Nik at Ceriatone and ask him about a Bluesbreaker kit as you seem to be asking about one in your profile. Their prices are reasonable.
thank you , just now seeing this, cool i have a parts head another b52, my buddy said hang on to it , might be able to use it for homeadid head,my friend back home has a machine shop said he would help with chasis
 

jammindude

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I suggest that you should consider the potential / likely reasons why the PT was getting so hot as to damage it. eg how much HT and heater current were the output valves drawing?
As you’re thinking, it would be extremely regrettable for its replacement to go the same way.
Were all the fuses the correct spec?
It’s a rather unusual PT, did you use an exact ‘like for like’ replacement?


Have you got it oriented correctly, ie such that the pick transducer isn’t directly underneath the PT?


What output valves have you used, and how did you check that the bias was appropriate for them?


Compared to your current amp, that’s as different as chalk and cheese, or at least as much as any 2 valve guitar amps can be! Are you sure about aiming for such an extreme change?
are you talking about reverb tank or pt, did not replace, just put a fan on my newer one, yes to correct fuses, asked tech how it burnt out, he said egnater did a good design but chinese cut corners on pt and internal wires melted together, but i do not see it, i dont think the reverb tank above the power tubes is a good idea so i might build a seperate box for tank, thanks for the reply, Jan
 

jammindude

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I suggest that you should consider the potential / likely reasons why the PT was getting so hot as to damage it. eg how much HT and heater current were the output valves drawing?
As you’re thinking, it would be extremely regrettable for its replacement to go the same way.
Were all the fuses the correct spec?
It’s a rather unusual PT, did you use an exact ‘like for like’ replacement?


Have you got it oriented correctly, ie such that the pick transducer isn’t directly underneath the PT?


What output valves have you used, and how did you check that the bias was appropriate for them? it haS 4 SOVTEK 5881 WXT


Compared to your current amp, that’s as different as chalk and cheese, or at least as much as any 2 valve guitar amps can be! Are you sure about aiming for such an extreme change?
 

Pete Farrington

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are you talking about reverb tank or pt
Sorry I wasn’t clear, I’ve edited my earlier post #42 to try and eliminate any ambiguity.
Let me know if it’s ok now :)

does anyone know what else i can do besides a fan in the back to draw the heat away from PT, that is what killed my last one

are you talking about reverb tank or pt, did not replace, just put a fan on my newer one

asked tech how it burnt out, he said egnater did a good design but chinese cut corners on pt and internal wires melted together,
i have a parts head another b52
From the above, what exactly has happened seems confused, but from what I can make out, the PT in your amp failed, and has been replaced, using the PT from another amp of the same / very similar, type.
The replacement PT is getting hot, so a cooling fan has been installed somehow.
But you’re still concerned about it getting hot.
Is all that correct?

Has the reverb tank failed? If so, has it been replaced?

it haS 4 SOVTEK 5881 WXT
Ok, so they will dissipate less filament heat than eg EL34, KT66.
But the most significant aspect of the heat from them will be their anode dissipation at idle.
That is controlled by the bias adjustment.
And that applies exactly the same to any type of output valve. ie their idle anode dissipation should be checked to ensure that the bias setting is suitable.
If the bias setting allows them to draw too much HT current from the PT at idle, then the PT will get too hot.
 

myersbw

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And, to expand on what Pete said regarding bias, this amp is camping on a lot of preamp overdrive.Thus, you can bias the output tubes a bit on the cool side and not sacrifice tone. (And, gain a bit of tube life longevity.) I'd shoot for a 50-55% idle bias and see how that works.
 

jammindude

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I REPLACED THE REVERB TANK NOT THE PT, LUCKILY MY GOOD B52 HEAD HAS A MOD BEING A POT FOR ADJ BIAS, DID IT BY EAR WAITING FOR A BUDDY TO COME OVER AND SET IT , I JUST PUT IT AT CENTER THAN ADDED JUST A TAD SO NOW IT DOESNT BREAK UP AT LOW VOL, SOUNDS AWSOME,
 

PelliX

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I REPLACED THE REVERB TANK NOT THE PT, LUCKILY MY GOOD B52 HEAD HAS A MOD BEING A POT FOR ADJ BIAS, DID IT BY EAR WAITING FOR A BUDDY TO COME OVER AND SET IT , I JUST PUT IT AT CENTER THAN ADDED JUST A TAD SO NOW IT DOESNT BREAK UP AT LOW VOL, SOUNDS AWSOME,

Contrary to popular belief, CAPS lock is not the cruise control of cool, but alright. :D Adjusting bias by ear without meters attached is not a recommended way of going about it, especially considering the way this amp is designed.

he said egnater did a good design but chinese cut corners on pt and internal wires melted together

So, it still has the original PT, the one that had internal wires melted together? And it's getting hot again? I think what @Pete Farrington is getting at, is that the PT overheating has a cause, and one should address that, not the fact that the PT is getting hot as such. If it's really a piece of junk PT that for no external reason is starting to melt/short, etc - then replace it. Now. If the draw on it is unreasonable, then that should be corrected.
 

Pete Farrington

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chinese cut corners on pt and internal wires melted together

I REPLACED THE REVERB TANK NOT THE PT
Sorry but I’m having trouble making sense of what you’ve writing.
What component had wires that melted together?

Regarding bias adjustment, it should be done in the ‘solid state’ mode.
The schematic I linked to previously shows VR18 as a bias adjustment trimmer. Was that not fitted to your amp?
https://music-electronics-forum.com/filedata/fetch?id=812574
Note that adjusting the bias trimmer will have no effect when in the ‘class A’ mode.
 

jammindude

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somebody put a bias mod on back it looks like a input jack but has a slot to adjust , dont know enough to mess with actual bias trim inside
 

jammindude

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talking about a diff. amp my second b52 , replaced reverb and it works fine, using fan so i do not have a repeat of what happened to my other, having someone adj the bias, thanks for reply, as far as power tubes i still have stock sovtek 5881, was asking if there is another i should use that does not run as hot
 

jammindude

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Hello , i sold the b52 head, and cab, i just landed another, this one is the at100 212 combo, which is supposedly hotter, i got it sooo cheap , i traded it for a berhinger v tone that i paid 25.00 for, it was in pcs and i luckily put her back together and it sounds great, but no clean channel, he told me i needed to put a new volume pot, so i did install it and nothing, the reverb dcidnt work, i have 2 tanks leftover and lots of spare parts from the first b52 i had, and i got great reverb, sorry to see this one does not have a bias adj pot on the back of amp, if it is easy i would like to install one on this one, speakers sound great, b52-at1216 16 ohm 120 watts, and i got a mint crate cab today loaded with celestion 30s delivered for 50.00 yehaaa, i dont care what anyone says about these made in england 30 watt speakers, i think they sound better than anything else i had, except a marshall 4/10 celestions .....right now i am wiring up some fans to draw out all that heat, need help with bias please, Jan p.s i got a speco tech pl200m amp for free, can i use any of the transformers in these to use for diy tube amp???
 

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