Need help with Linn Valhalla repair

I'm hoping somebody can help me out; I've serviced my (previously working) valhalla board as per advice on this thread:
replaced all the electrolytic caps on the board, like for like, 47uF caps increased to 450v
R2 and R3 changed for 7watt wirewounds.
Upgraded the bridge rectifier to a Vishay 6 amp 1000 volt
Replaced R1 with an NTC 50R, 1.9A thermistor
Replaced C16 with 2 paralleled 0.1uF

On powering up, R 26 (3R 0.25 watt) immediately blew with much smoke. :(

The PCB fuse did not blow, and no other damage is visible.
Subsequent checks showed a dry joint on the rectifier, which I've corrected.

I'm now waiting for the replacement R26 to be delivered, however I'd greatly appreciate it if a DIY expert could point me in th right direction and advise if the rectifier dry joint is the likely cause of the R26 failure, also is any other component likely to be affected?

Here's the schematic (mine's a early Valhalla without V1,V2, D3 and R40 as noted on the schematic)

https://elektrotanya.com/linn_valha..._motor_control_pcb_1989_sch.pdf/download.html

Thanks in advance
Bryan
 
Thanks and well spotted. The dangersof posting after a tipple or two...
Yes I did mis-type C16, but this should read C19, which is shown as 0.2u
I've no idea where my R26 3ohm came from. You are correct, it's 22R as you say, and fortunately, that's what I had ordered to replace it...
The cold joint on the rectifier is fixed so I'll fit the replacement R26 and see what happens when it's powered up...
 
I tried replacing R26 whilst waiting delivery of BUX85G from Farnell. It failed immediately, as expected really.
The BUX85G's arrived, so I replaced Q2,3, 4 and replaced R26.
I left the switch and motor disconnected and powered up
Result: R26 burned out immediately, but this time, the fuse, 1 amp quick blow, also failed, which has not happened before. No other visible damage.
I've rechecked all component values, orientation, solder bridges and dry joints. All appears OK.
Any further advice would be greatly appreciated, I'm not sure where to go from here.
 
I tried replacing R26 whilst waiting delivery of BUX85G from Farnell. It failed immediately, as expected really.
-----------snipped-------------
Any further advice would be greatly appreciated, I'm not sure where to go from here.

There's a possibility of Q11, Q22 and D2(1N4148) is defective. You may have to replace that transistor array IC MC3346 (or equivalent at schematic). MC3346 is an obsolete part but NOS alternatives could be available. If Q3 or Q4 is short circuited, the high voltage will take out the transistor array IC, and D2 instantly. Ensure all the power transistors are perfect, replace MC3346, and diode, R26, it should work. If fuse blow or no startup torque to 85V (with motor connected), then something else at the power amp section isn't right.
 
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Thanks Coolmaster. I've also been advised that I've made a mistake by not soldering the -ve lead of C3 to the board topside conductor. i will do this, retest and replace as necessary, and try again....

This is a picture of mine from quite sometime ago. Its show C3 soldered to the upper plane.
 

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Yes, I got it working again, components changed were those previously posted.
Here are the steps I followed, many thanks to neiljadman on another forum
Solder C3 correctly to the top side in addition to the underside.
Replace R26 Making sure to solder the top side connection here too!.
Remove, check and replace D2 as necessary (any generic 1N4148 diode will do).
Test R24 and R37 in circuit, replace as necessary
Remove, test and refit or replace TR4 as necessary (plenty of info on the web as to how to).
Fire it up and see if it works - it will not flare up
Remove, test and refit or replace TR2/3 as necessary
Fit new IC1 and try again
 
Thanks for the reply.
My problem was caused by failing to solder top side of C3.Re soldered C3 and then
Replaced all the parts you mention above, doesn’t blow the fuse now but still not working.
Only difference is that I used BUL45D2G to replace TR2,3,4.
Can anyone tell me if my choice of transistors is ok ?
Any help would be much appreciated.
 
Hi, I used BUX85G on the recommendation from another forum. I'm not sure whether your BUL45D2G is a direct replacement for the original, however here's a link to the schematic, which shows a few substitutions.
http://www.turntablepsu.com/images/valhalla schematic.pdf
Not sure where you are based, but if in UK/Europe, here's where I purchased the BUX85G £1 each.
BUX85G | ON Semi BUX85G NPN Transistor, 2 A, 450 V, 3-Pin TO-220AB | RS Components
Have you replaced R1 and upgraded the bridge rectifier? Apparently the rectifier is prone to damage.
Google 'valhalla meltdown' to see the guidance I was given. Having said that, this thread probably has all the info you need already...
 
I’ll check out the BUX85G and will probably change the ones I have.
I started out replacing the three big electrolytic capacitors , rectifier and R1( I fitted the SG240 varistor (?). Also did the diode mod for the motor.
Decided to replace all the electrolytics and that’s when my problems started.
After popping the fuse and burning out R26, I Searched forums and found the C3 solder info.
I’ve been chasing the fault ever since.
Also replaced D2 diode, tested another couple of resistors and replaced IC1.
Don’t know where to go next.
Maybe abandon the Valhalla and build an Armageddon clone?
 
Was it working before you started working on it?
When I burned out R26, it took TR2 and TR4 with it.
Did you solder R26 as well as C3 to the top plate?
I'd also re-check all your soldered connections- I checked mine using a DMM and found a high resistance/dry joint on a rectifier leg.
Also check for any solder shorts across tracks?
You could also try posting on the valhalla meltdown thread I started, there are some very helpful and knowledgeable people watching it.
good luck
 
Update on my previous post.
While I am deciding what to do with the Valhalla, I built an Armageddon clone.
Got it hooked up yesterday to test it and with a bit of capacitor matching it’s up and running.
I’ll test it for a few weeks, while I work on the wooden enclosure.
First impressions are really good & I might not go back to the Valhalla!
 
Valhalla update

Just thought I’d update my post.
Hopefully I’ve managed to include some photos, two of my Armageddon power supply and the other of the LP12 wiring conversion.
More than enough happy with the performance, so I’ll leave the Valhalla repair for now!
 

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I recently installed a Vinyl Passion Revolution power supply for a client in an Ariston RD 11S (forerunner to the LP12). It's a great little electronic speed control designed for the LP12 that ramps up the frequency and/or voltage to the motor at start or speed change. A highly recommended replacement for Valhalla or Hercules II supplies, and vastly superior upgrade to simple resistor / phase capacitor type supplies because it optimises motor torque smoothness and removes unstable mains frequency from pitch control.

The Vinyl Passion Revolution Power supply
 
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