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Joe
10-06-2009, 19:08
My Border Patrol power amp, which had new valves and various other bits of TLC about this time last year, has developed the same fault again (a crackling noise in one channel). I'm less than pleased, to put it mildly, and am seriously thinking of going ss. Before I make an irrevocable decision, does anyone know of a reliable valve amp mender in the Bristol area?

Cheers

alb
10-06-2009, 19:22
Could it be something simple like grubby valve pins?
Forgive me if you've tried the obvious things already.

Joe
10-06-2009, 19:26
I've checked that; unplugged, cleaned pins and re-installed all valves, which given my lack of DIY skills just about exhausts what I can safely do!

pure sound
10-06-2009, 21:26
I take it you've sent an email to Gary at Border Patrol?

bp@borderpatrol.net

If you swap the Left channel & Right channel output valves, does the crackle switch sides?

Anthony at Tube Distinctions isn't a million miles away
http://www.tubedistinctions.co.uk/contact_info.htm

Ian Walker
10-06-2009, 21:50
Sounds like same prob a friend had recently,turned out to be a solder joint had come adrift from valve pins...do you do a lot of tube changing?

Marco
10-06-2009, 22:18
Yep, that was me :)

Joe, it could be that one of the resistors soldered onto the base of the valve seats has become disconnected as a result of plugging and unplugging valves or that one of your valves on the channel which is crackling has developed a fault.

To find out if my first suggestion is the cause you need to remove the base plate from your amp (make sure it's unplugged from the mains first), look inside, and check all the connections on the valves relating to the channel where the crackling noise is coming from. You should be able to see straight away if anything has become disconnected. If so, either re-solder it yourself, if it's obvious where it goes, or get someone competent to do it for you.

If it's a faulty valve then all you need to do is get hold of another one of the same type and pop it on in place of the faulty valve, and see whether the crackling noise goes away. However, as a long-term safe solution you may have to buy another matched set of valves of the same type, as the new one you've put in may not measure the same as the others and thus be incompatible with the circuit. It depends if your amp has been designed to use matched sets of valves or not.

Hope this helps. Let us know how get on :cool:

Marco.

alb
10-06-2009, 23:07
Joe.

A word of warning just in case you do decide to have poke around inside it.
It's possible that there may be charged capacitors inside with potentially dangerous voltages.
Although i would encourage people to have a go at faultfinding, if you don't feel comfortable with electronic parts, then it may be prudent to find someone who knows their way around these things.
Can't help thinking the problem is likely to be something quite simple though.

Marco
10-06-2009, 23:28
Yes, good advice there from Al :)

Always be very careful where live voltages are concerned!!

I think it's something simple too, as I have outlined.

Marco.

Spectral Morn
10-06-2009, 23:37
It could also be a capacitor. I had a similar sounding problem with my BAT VK75 last year and thats what it turned out to be. Tried valve swopping etc and at the end of the day it was only when Rodney Hanna (the engineer I use )had a look that it turned out to be an intermittent fault with a capacitor. He commented how scary the BAT was to work on, as it had to be on to help find the fault. "Those capacitors wanted to kill me" he joked. There are lots of these in BAT products.

Stick with the Border Patrol amplifier SS can be very good but there is a quality to valves that most SS can't match....the slight hassle is worth it IMHO/E


Regards D S D L

Primalsea
11-06-2009, 07:15
If swapping the valves around doesn't identify the fault the next thing I would do is a visual inspection inside the amp after it has been off for a whole day.
If there is nothing obvious I would then put on a pair of thick rubber gloves get hold of a 6mm x 150mm wooden dowel or similar (anything non conductive), turn the amp on and prod the various solder joints with the dowel. If its a dodgy joint you will here the crackle through the OLD pair of speakers you have connected to the amp.

Not everyone is comfortable with working on electronics but if you decide to have a go just be careful and think before you do anything. Its often the silly things like having you mug of tea next to you that let you down.

Clive
11-06-2009, 13:45
Chop sticks are a useful prodding tool.

Is the amp PP or SE? Does it have a penode on the input?

PP may want a load connected to the output (speakers, maybe not your best!) and pentode will want the input shorted.

Ian Walker
11-06-2009, 15:27
If there is nothing obvious I would then put on a pair of thick rubber gloves get hold of a 6mm x 150mm wooden dowel or similar (anything non conductive), turn the amp on and prod the various solder joints with the dowel..

I would actualy go even further than that and shlip into a full rubber skin diving suit,the heaviest rubber wellies you can get your hands on and suitable ex manweb industrial rubber gauntlets.Then i would nip down to the local pet shop and buy a one of those solid rubber dog bones(to bite on) and a strap,then i would er heee err haaaaa :lol:

Spectral Morn
11-06-2009, 15:39
I would actualy go even further than that and shlip into a full rubber skin diving suit,the heaviest rubber wellies you can get your hands on and suitable ex manweb industrial rubber gauntlets.Then i would nip down to the local pet shop and buy a one of those solid rubber dog bones(to bite on) and a strap,then i would er heee err haaaaa :lol:

You have been round to Marco's to often Ian. Was this your reward for carrying Marco's new Tannoys up the stairs;):lol::lol::lol::lol:



Regards D S D L

DSJR
11-06-2009, 15:57
Just to add that before the cap-resistor mod Glenn told me to do on my preamp, the two large reservoir caps held their charge for WEEKS as there was nowhere for the stored energy to go once powered off.

If you wish to delve around safely, make up a capacitor discharge tool (an insulated resistor [forget the value] with two soft instrument wire extentions and terminated in croc clips). These can be safely placed on the caps (supply well and truly disconnected) to gradually discharge them safely.

If there's the slightest doubt, get an expert engineer to check things over.

Joe
13-06-2009, 18:38
Thanks for all the hints/tips. I'm not about to go poking my amp with sticks or wielding a soldering iron.

However I did, as suggested, swap the valves over and ... the crackle has gone! I played 3 albums straight through, and not a hint of a crackle. So, fingers crossed, simply swapping the valves seems to have done the trick.

Marco
13-06-2009, 22:17
Nice one, Joe. I thought it was something relatively simple :)

If the culprit was dirty valve pins, you should clean them all with a fibreglass pen (available at many places on-line and on Ebay), and then remove any excess grunge with some cotton wool buds and isopropyl alcohol.

It pays to keep them in tip-top condition :cool:

Marco.