Peavey valveking royal 8 trouble,need help

ANBU

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hi,i have a peavey valveking royal 8 single ended class-a tube amp.it has ECC83 preamp tube and EL84 power tube.and stock 8'' 8ohm speaker.

i didnt like the stock sound of it,because the speaker just doesnt sound nice,and the soudn is a lil bit muddy and bassy.so i thought to do modification on the preamp circuit.firstly heres the attachment schematic of the amp.

heres the changes i made with the resistor and capacitors:
R16 - to 10k
r10 - to 1k
C1 - to 1uF
C6 - to .047uF
r5 - 240ohm
c4 - put it up to 2uf but put it back to original value
C2 - put it up to 100uF but put it back to original value

as a result i got better sound,nice crunch overdrive,better treble response.

i didnt change the components i one session,but in about 5 session,as i wanted to check the sound changes.

on the last modification,i accidentally put the preamp tube on the powertube socket,and for the powertube,vice-versa.i realised this when i turn on the amp and i notice a funny smell.so i hurriedly turn the amp off.and opened up the amp again,check if the fuses were blown,but not.resistors and caps,none burned,so i wonder where the smell came from.

because i panicked,i accidentally touched the pc board and BOOM+SPARK,got shocked badly several time(i forgot to drain the current of the lage caps).well,that aside.i put the back the tubes,in the right sockets.

then i put everthing back together.turned on the amp,the tube lit up fine.but what i noticed is the volume.i think there was a loss of about 95% volume from the speaker.but when i put the headphone,it fine,the volume goes loud normally as before and the tone wasnt affected.

so,i was confused what may have gone wrong.i dont feel like bringing it to a technician unless its the last resource.because i dont feel like paying for a repair for an over E100 tube amp,if they are to charge for a repair @ half the amps price or more.

well,any experts have suggestion?or any generous person who would like to help a poor student here?lol.

oh another question.is the amp self-biasing or fixed biased?theres no trimming pot on the pc board for biasing.

i hope to get help from you guys

landsleaving

Sounds like you blew the speaker. Have you tried connecting it to another one, or a cab?

Thats a nasty shock isn't it? I screamed like a 3 year old girl when I got one!

ANBU

well,i do hear volume from the speaker,but its very low.,the tone wasnt affected.no i dont have any other speakers and the amp have no cab jacks.
i took out the speaker and connected it to the laptop,and it had no problem playing mp3 at the loudest the laptop volume can produce.so i think it may not be blown speaker.

also im trying to figure out where the funny smell came from when i misplaced the tubes.no resistors or capacitors where burnt,and the solder joints are fine.

ye,it kinda hurt getting shocked,but not as bad as when i got electrocuted when i was 5yo,i fell uncouncious for 5 hours.

Paolo_M

This amplifier is cathode biased which is self regulated, there is no bias adjustment necessary or even possible without modfying R8. 150 ohm is about right for the plate voltages in this amp.


I would suggest that the best mod for this amp is to install a speaker out to allow you use an external speaker.
I'd also question R17 and VR3 if they are the values shown. They would roll off a significant amount of highs producing a quite muffled tone. This is where I'd start before modding anything in the preamp.

If you installed the preamp valve in the power valve socket the you most likely have destroyed the preamp valve. They're rated for 1 Watt and a single ended amp tries to idle at 12 Watts.
The power valve may also be damaged as I think you've put Ht across the heaters if you put it in the preamp socket. The pin assignments are completely different.


This amps is not 8 watts by the way, it's actually 5 watt but that's just a by the by.


The schematic is also incorrect as it shows the speaker being disconnected when the headphones are in use, which either a. is incorrect or b. the amp blew up a long time ago. I'm wondering how much of the rest is incorrect too.

Can you post pics of what you've as it might make things clearer?

ANBU

yeah,i never intended to change r8 anyway.

well,about the valves and socket mistake,both preamp and power tubes have similar pins each.well heres the pic.as you you can see the pins have same lengths and number,so no wonder they both fit on each socket.

i think the schematics is alright because the diagrams correspond with the actually pc board of the amp.i have no doubt about it as it came directly from peavey.heres the inside of the amp(i just got it from the internet).also if you wana compare if to the epiphone valve junior i have the schematics.the diagrams kinda look close to each other.

well im also skeptical about the r17 but i dont know the effects of changing it to higher/lower resistane value,but right now i dont wanna touch the amp until im sure whats causing the huge loss of volume to the speaker and the possible source of that funny sterile smell when i accidentally place the valves in wrong sockets.

darrenw5094

Paolo_M wrote: »

This amplifier is cathode biased which is self regulated, there is no bias adjustment necessary or even possible without modfying R8. 150 ohm is about right for the plate voltages in this amp.


I would suggest that the best mod for this amp is to install a speaker out to allow you use an external speaker.
I'd also question R17 and VR3 if they are the values shown. They would roll off a significant amount of highs producing a quite muffled tone. This is where I'd start before modding anything in the preamp.

If you installed the preamp valve in the power valve socket the you most likely have destroyed the preamp valve. They're rated for 1 Watt and a single ended amp tries to idle at 12 Watts.
The power valve may also be damaged as I think you've put Ht across the heaters if you put it in the preamp socket. The pin assignments are completely different.


This amps is not 8 watts by the way, it's actually 5 watt but that's just a by the by.


The schematic is also incorrect as it shows the speaker being disconnected when the headphones are in use, which either a. is incorrect or b. the amp blew up a long time ago. I'm wondering how much of the rest is incorrect too.

Can you post pics of what you've as it might make things clearer?

+1

Paolo_M

ANBU wrote: »

yeah,i never intended to change r8 anyway.

well,about the valves and socket mistake,both preamp and power tubes have similar pins each.well heres the pic.as you you can see the pins have same lengths and number,so no wonder they both fit on each socket.

i think the schematics is alright because the diagrams correspond with the actually pc board of the amp.i have no doubt about it as it came directly from peavey.heres the inside of the amp(i just got it from the internet).also if you wana compare if to the epiphone valve junior i have the schematics.the diagrams kinda look close to each other.

well im also skeptical about the r17 but i dont know the effects of changing it to higher/lower resistane value,but right now i dont wanna touch the amp until im sure whats causing the huge loss of volume to the speaker and the possible source of that funny sterile smell when i accidentally place the valves in wrong sockets.

They have the same pin style but the pin assignments are very different. I suspect that you have damaged at least one of them.

Did the HT fiuse F1 blow?

Do you have a multimeter?
If so then remove the power valve and measure the DC resistance between the blue and red OT wire.
What value are you reading? 0 is not good and anything over around 300 for this OT is not good. Anything in between means your OT is probably ok.
Your OT may be causing the smell as the preamp valve would have a vastly different output impedance than the power valve.
Burnt windings don't smell plesent.

As I suspect that you've also damaged your valves you may need to replace them. But not until you establish that the rest of the circuit is healthy.

1Meg in series with the output valve (there's also a 47k grid stopper plus whatever the volume pot puts in series will cause massive high end roll off. It needs to be reduced significantly. It also is well above the maximum grid leak resistance value for the EL84.
Personally I'd replace R17 and the volume pot with a single 250kA pot and a 10k grid stopper. Even then you'd probably need a treble bleed for lower volumes.
However I still doubt that the schematic is correct, it's not unusual from manufacturers to include errors for various reasons. Can you confirm these values are the installed values?

Let us know how you get on with the OT readings and we'll go from there.