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Search: Posts Made By: John Caswell
Forum: General 7th November 2018, 04:46 PM
Replies: 6
Views: 142
Posted By John Caswell
Re: Earthing questions

Hi Stuart
Definition - chassis is metalwork earth directly connected to power line earth
Signal earth - signal earth which could be isolated from chassis via a 10-100R plus a 0.1F in parallel or...
Forum: General 7th November 2018, 01:24 PM
Replies: 6
Views: 142
Posted By John Caswell
Re: Earthing questions

Hi Stuart et al
The simple answer is yes purely on safety grounds.
Earthing volume controls immediately alleviates the problem of hum from fingers when using the v/c if it has metal knobs.
Because...
Forum: WD Amplifiers 20th October 2018, 12:01 AM
Replies: 29
Views: 652
Posted By John Caswell
Re: WD88VA didn't survive move

Hi all,
With general use I don't give output valves more than a couple of years life, as they really get hammered in amplifiers, so these two sets have done remarkably well!
With EL34, KT88, 6550...
Forum: WD Amplifiers 19th October 2018, 05:21 PM
Replies: 29
Views: 652
Posted By John Caswell
Re: WD88VA didn't survive move

Hi all,
Wiggers amp sorted.
When the first KT88 blew up it took out the bias capacitor short circuit and fried the screen grid suppressor resistor, so putting in a new valve just over ran it....
Forum: WAD General 19th October 2018, 11:47 AM
Replies: 2
Views: 190
Posted By John Caswell
Re: Heater wiring for twin rectifiers

Hi Greg,
Whilst there is some evidence this helps when used in output stages, be it PP or SE I cannot see it making any real difference on power supplies. I suppose the best I can answer is it's...
Forum: WD Amplifiers 19th October 2018, 11:42 AM
Replies: 29
Views: 652
Posted By John Caswell
Re: WD88VA didn't survive move

Wiggers you have a PM

John
Forum: WD Amplifiers 17th October 2018, 04:01 PM
Replies: 29
Views: 652
Posted By John Caswell
Re: WD88VA didn't survive move

Hi Wiggers,
Yes that's the correct address etc.
Let me know what you want to do.

John
Forum: WD Amplifiers 17th October 2018, 03:14 PM
Replies: 29
Views: 652
Posted By John Caswell
Re: WD88VA didn't survive move

Hi Wiggers,
Yes still am, do you wish me to have look at it?
Was the flash and pop from the same valve position or the other one on that side.
If so you may have had another faulty valve, not...
Forum: WD Amplifiers 14th October 2018, 10:23 PM
Replies: 29
Views: 652
Posted By John Caswell
Re: WD88VA didn't survive move

Hi Wiggers et al,
Oh I haven't left the forum, I just keep a slightly lower profile now as others are more than capable of answering the questions that pop up.

John
Forum: WD Amplifiers 14th October 2018, 03:12 PM
Replies: 29
Views: 652
Posted By John Caswell
Re: WD88VA didn't survive move

Hi Wiggers ,
Don't panic Mr Mainwaring it is most likely to be a valve shaken up by the move and possibly a bit of cathode material worked loose.
If you have a spare valve stick it in, but not...
Forum: WAD General 5th October 2018, 07:04 PM
Replies: 9
Views: 255
Posted By John Caswell
Re: KT5881 valve change

Hi all,
Yes, apologies, I did not make my intention clear that it was heater current I was discussing.
Gary, Yes the Quad amplifier will accept KT66, 5881, 6L6 and 6P3P because its heater current...
Forum: WAD General 5th October 2018, 04:12 PM
Replies: 9
Views: 255
Posted By John Caswell
Talking Re: KT5881 valve change

Phil et al,
Built my first amp when I was 9 albeit with a bit of help, I'm now 77 and still learning, but apparently still "don't know nuffin" as I am constantly contradicted by self professed...
Forum: WAD General 5th October 2018, 03:08 PM
Replies: 9
Views: 255
Posted By John Caswell
Re: KT5881 valve change

Hi Gary,
This is not a substitution I would recommend, purely on the grounds of heater current consumption.
The 5881 is rated at 6.3v 900ma whereas the KT66 is rated at 6.3v 1.3A. This is well...
Forum: WD Amplifiers 11th September 2018, 11:35 AM
Replies: 2
Views: 228
Posted By John Caswell
Re: WD phono load

Hi Phil,
The output impedance of the Phono 2/3 is approx 4K, so I would not run it into less than 10X as much ie 40K.

John
Forum: General 18th August 2018, 10:53 PM
Replies: 19
Views: 1,534
Posted By John Caswell
Re: A gun, wax and hearing problems.

Hi Bob et al,
This of course is the main problem with all hearing aids, you go from something that can differentiate sounds around, to basically a point receiver (the microphone) so it takes some...
Forum: WD Amplifiers 18th August 2018, 05:21 PM
Replies: 9
Views: 453
Posted By John Caswell
Re: Where to buy valves

Hi Mel,
I see you r point they do not do 6P14P and I am not sure who you would be able to get a matched set/pairs of those from as I don't know of anyone who imports the Russian variety.
You may...
Forum: WD Amplifiers 18th August 2018, 11:19 AM
Replies: 9
Views: 453
Posted By John Caswell
Re: Where to buy valves

Hello Mel,
Don't waste money on buying matched ECF80/E80CF/6BL* or their CV equivalent CV5215 they are so variable - see my comments and FAQ.
I suggest Hotrox in Nottingham for EL84/6BQ5/6P14P....
Forum: General 18th August 2018, 10:22 AM
Replies: 19
Views: 1,534
Posted By John Caswell
Re: A gun, wax and hearing problems.

Hi all,
Had mine checked a couple of years ago, usual problem about 6dB down at 8KHz, possibly more.
Went to Royal Berks Audiology Dept. in Bracknell which is apparently the best locally and was...
Forum: For Sale 30th July 2018, 12:46 PM
Replies: 25
Views: 1,386
Posted By John Caswell
Re: FS WAD 300b with mods

Hi Adrian,
Yes I agree with what you say, from the picture is was not easy to see whether the 15R were in parallel or not.
As the "cathode bias" R is 1K5 this will reduce the current allowed so the...
Forum: For Sale 30th July 2018, 09:55 AM
Replies: 25
Views: 1,386
Posted By John Caswell
Re: FS WAD 300b with mods

Hi all,
As I see it, according to the colour code on the green resistors, it appears to be a 1K5 paralleled with a 15R (Brown, Green, Black) which is definitely wrong.
Adrian I think your sums are...
Forum: For Sale 29th July 2018, 01:26 PM
Replies: 25
Views: 1,386
Posted By John Caswell
Re: FS WAD 300b with mods

Gentlemen,
This thread is drifting off topic.

John
Forum: WD Amplifiers 26th June 2018, 09:36 AM
Replies: 7
Views: 489
Posted By John Caswell
Re: WAD CF Pre relayboard not working Help

Hi Colin et al,
Although I am not normally into violence I have to admit a good slap often helps gel the brain:D
Nicely done Colin

John
Forum: WD Amplifiers 25th June 2018, 06:41 PM
Replies: 7
Views: 489
Posted By John Caswell
Re: WAD CF Pre relayboard not working Help

Hi Colin,
1) Did it work originally?
2) Is the 6.3 v supply the correct way round, because the LED is not lit up, which could mean that the heaters supply is the wrong way round.

John
Forum: WAD Problems 17th June 2018, 12:19 AM
Replies: 2
Views: 301
Posted By John Caswell
Re: KiT/KaT6550 and fuse blowing inrush current

Hi Greg,
Yes this item is fine and as Farnell says a suitable replacement for the original.
Just remember to mount it on longish leads as it gets pretty hot and contrary to my general...
Forum: WD Amplifiers 7th May 2018, 11:09 AM
Replies: 5
Views: 464
Posted By John Caswell
Re: Converting WD KT88 to XLR

Converting the WD88 to balanced inputs is a relatively simple job.
There are two ways of doing it either electronically using a dedicated unbalanced to balanced IC, or using a 1:1 transformer...
Showing results 1 to 25 of 1453

 
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