Valveking II 50watts combo schematics

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johnxue28
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Valveking II 50watts combo schematics

Post by johnxue28 » Sun May 09, 2021 1:55 pm

Hi, need schematics for this amp. The F2 fuse keeps blown and I cannot find schematics for this amp.

Thanks

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JamesPaul
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Re: Valveking II 50watts combo schematics

Post by JamesPaul » Tue May 11, 2021 12:37 am

johnxue28 wrote:
Sun May 09, 2021 1:55 pm
Hi, need schematics for this amp. The F2 fuse keeps blown and I cannot find schematics for this amp.

Thanks
I have seen the VK II 20 and 100 schematics here on the forum, but not the 50. If you call Peavey Customer Service and ask for the schematic, they used to email it to you that day.

I am not certain Peavey has fully caught up from the backlog due to COVID, but try calling a few times if you are getting voicemail. I have seen other posts here where Peavey is still behind on answering email, so if you can, a call is likely better.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

rogue777
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Re: Valveking II 50watts combo schematics

Post by rogue777 » Fri May 14, 2021 7:40 pm

Not exact, but this should work. Thanks to Low Tom for posting this.
Attachments
valveking2-100d (1).pdf
(122.98 KiB) Downloaded 394 times

johnxue28
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Re: Valveking II 50watts combo schematics

Post by johnxue28 » Mon May 17, 2021 11:13 am

Hi, thank you for the schematic, I want to give some update on this.

I used this schematic to trace the fuse blown out problem. And tested most of the components and found no short issue.

So I put everything back and only put one 6l6 tube on, and measured the bias, here was what I got:

Plate voltage: 505v
Screen voltage: 500v
Cathode voltage:75v
Transformer output: 370 v rms

The fuse is not blown, but the tsi will turn green for several seconds then back to red.

So I think it is not short circuit issue, but I am not sure it is related to tube or power transformer. As the plate voltage is bit higher than I thought.

As noted in 100 watt schematics, the transformer output is 350v rms only, how can it be 370v on 50watt?

I still need schematic for 50 watt to confirm, call peavey customer support several times and sent emails as well, but no response yet.

By the way, I also tested 2 tpc fuse f104 and f105 connected to the power tubes, one is 1.6 ohms and one is 2.2 ohms, not sure if they are good or not.

Thanks for any suggestions

John

rogue777
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Re: Valveking II 50watts combo schematics

Post by rogue777 » Tue May 18, 2021 5:22 pm

If F2 blows the most probable cause is a faulty power tube.

The circuit is not designed to run on one tube. The voltages on the schematic are for two tubes under normal operation. Its an unregulated power supply so of course, with low current draw like in your setup the plate voltage goes up. I hope with the fuse and the internal protection circuit that no other components are damaged, like the screen, grid, and cathode resistors and R86.

Buy two new power tubes as a matched pair, and replace both the old power tubes with the new pair.
Proceed with the TSI adjustment.

johnxue28
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Re: Valveking II 50watts combo schematics

Post by johnxue28 » Tue May 18, 2021 7:43 pm

Thanks Rugue

Finally I got schematic for 50watt. From the schematic, I noticed several thing that is interesting,

1. The transformer output is 350vdc
2. The F2 fuse is t1.0a , not t0.5a, Pcb printed as t0.5a, so I used the t0.5 replaced, it definitely does not work. See the picture.
3. The 2 tpc fuses have been upgraded from 0.17a to 0.25a by peavey to prevent the hot tube causing the over current issue. Mine amp is not upgraded, still 0.17a fuse.

I am going to replace the F2 fuse with right one t1.0 first, then I will check the result. Will keep you updated.

Thanks a lot
Attachments
F2 fuse is marked wrong value on pcb
F2 fuse is marked wrong value on pcb
D2EEF8E3-CB65-4F04-881B-1F3A74B7BAEF.jpeg (463.02 KiB) Viewed 5467 times

johnxue28
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Re: Valveking II 50watts combo schematics

Post by johnxue28 » Fri May 28, 2021 8:28 pm

I’d like to give the update on how to fix my vk 50 eventually.

As noted before, the pcb borad marked wrong value for the F2 fuse, it is T1.0a on schematic and T0.5a marked on pcb. So I used to 1a time delay fuse, so it won’t blow up.

However, though the fuse is working, the TSI is not working, it still turns to red after short period of green light.

So I replaced the 2 resettable fuse connected to cathode of power tube. Note: the schematic marks these 2 psr fuse should be replaced to 0.25a from 0.17a. And mine is 0.17a still. And the resistance I measure is way too high. So I suspected they are bad.

So I replaced them with 0.25a, now I put everything back. Boo, it is working like a charm!

Refer to picture, you can see the 2 psr resettable fuse that I replaced.

Thank you all!
Attachments
Replaced 2 psr resettable fuses
Replaced 2 psr resettable fuses
3187997C-5E61-44DB-A569-1B661FF770E9.jpeg (1.36 MiB) Viewed 5414 times

Dart77
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Re: Valveking II 50watts combo schematics

Post by Dart77 » Fri Aug 20, 2021 9:26 am

Hi i allso have similar problem with my
Valveking vk2 50W combo. Only fuse is good but tsi is lighting red after few minutes if i push amp harder.
On low volume setings works fine and tsi lights Green.
Please can you send me schematic...
I tried with peavey customer supart but nothing...

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JamesPaul
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Re: Valveking II 50watts combo schematics

Post by JamesPaul » Thu Aug 26, 2021 10:26 pm

Dart77 wrote:
Fri Aug 20, 2021 9:26 am
Hi i allso have similar problem with my
Valveking vk2 50W combo. Only fuse is good but tsi is lighting red after few minutes if i push amp harder.
On low volume setings works fine and tsi lights Green.
Please can you send me schematic...
I tried with peavey customer supart but nothing...
If the TSI lights are only going red when you push the amp harder, that is most likely a bias issue or an indicator the tubes are wearing out. From the manual:

TUBE STATUS INDICATION (T.S.I.™) LEDS
These are LEDs that light green or red depending on the status of the power tube they are representing. These are merely the visual part of the wider status indication, fault detection and tube protection circuits. All models have one LED for each power tube, therefore all have two except for the ValveKing® 100 which has four due to it having four power tubes. From left to right these LEDs are associated with the corresponding power tube in the chassis.

The simple explanation is that the LED will be green in normal working mode and red in any other mode including: Standby, low bias, low current (tube wearing out) or high current fault condition that has switched on the protection circuit.

The more detailed explanation is as follows:

(This applies to all models but see below for important differences on ValveKing® 100.)

At Standby the LEDs should be red. This is due to the tubes not yet being fully on. When switching from Standby to On these should then turn from red to green. These should basically remain green in normal playing conditions.

If one or more LEDs goes red it means that tube is not working properly for one of the following reasons:

- Tube is ‘under current’: This could be due to incorrect bias, low current due to aging, open circuit due to structural/physical fault or missing filament heater supply.

- Tube has gone ‘over current’: In this case the resettable protection circuit will be switched on to protect against further damage and to allow the amplifier to carry on working with the remaining tube(s). This could be due to bias failure, over-heating of the tube or other fault condition resulting in excessive current draw.

Reset: In some conditions, with an adequate gap in playing, the protection circuit will auto-reset and allow the tube to be turned back on. If the fault remains then the LED will stay red. In these situations, at a convenient point the amp should be turned off for a few minutes then back on again. If the fault is still there then the amp should be checked by a factory authorized technician for correct bias or faulty/worn out tube(s).

Differences on ValveKing® 100:

In the normal ‘100% power’ and ‘speaker enabled’ modes, this will work exactly the same as mentioned earlier. However, as the 25% and 5% power modes as well as the speaker defeat setting intentionally turns off one pair of power tubes (to reduce unnecessary heat), the inner two LEDs will be lit red when set to any of these settings. This is the T.S.I.™ circuit operating as it should, by indicating that these two tubes are not currently active.
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

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JamesPaul
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Re: Valveking II 50watts combo schematics

Post by JamesPaul » Thu Aug 26, 2021 10:40 pm

johnxue28 wrote:
Tue May 18, 2021 7:43 pm
...

Finally I got schematic for 50watt. ...
Is the 50W schematic file small enough that you could post it here? If so, please do and thanks!
Enzo wrote:I find if the amp is working, that is a good point to stop fixing it.
James Paul's Peaveys
Decade, Classics, Ecoustic, Windsors, VYPYR, Triple XXX, XXL, VKs, Bandit, JSXs, VIP, Piranha and a Penta.

elrrek
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Re: Valveking II 50watts combo schematics

Post by elrrek » Fri Nov 05, 2021 11:12 am

I'd also like to get a copy of that schematic, might solve my problems too!

CoolChange25
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Re: Valveking II 50watts combo schematics

Post by CoolChange25 » Sat Jan 21, 2023 5:39 pm

Could I get a copy of the VK II 50 schematic?
I have a VK II 50 with a pair of 6L6Eh power tubes. An hour into rehearsal the right TSI light went red and I lost most of the amps power.
I replaced them with a matched pair of Solvtek 6L6wx7. Now the lights are green but one of the tubes has a blue glow as the other is clear.
Is the VK II auto biased or could that be an issue? Thanks

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