WD KT88VA XL build (steamboat)

[steamboat]

Originally Posted by John Caswell

Hi S/Boat,
A few replies to help I hope.
I assume that you are measuring with the DMM earthy lead connected to signal earth not chassis earth. Is it an autoranging DMM?
IEC earth blade 4ohm should be 10 - check your wiring of the 10R/R27 earth lift resistor between LS earth terminal and chassis earth terminal
U1 pin 3 and 8 1.59ohm - OK
U2 Pin 3 and 6 9.99ohm - NO this should read 10K =10000R - Check R6
U3/U4 Pin 8 480R should be 470R - OK 470R ±5%
output power transformer Pink wire to 26/28 430AC should be 324AC - Don't understand this. If it is the HT feed to the OPTX primary centre tap it should be a DC voltage, However if it is the power transformer pink secondary wires, they have NO reference to earth and should read approx 320Vac pink to pink
Heater R28/R29 5.9-6.2 - would like to see this a bit higher see below
C17 5.8DC should be 5.9-6.3 - try changing R30 to a lower value to bring this voltage up to approx 6.3Volts
C13 450DC should be between 410/435DC - Likely high power line voltage, check power transformer tappings
C16 46.7DC should be 45v - well within tolerances don't worry
U1 Pin 223DC Pin6 210DC should be 185+-10% - Check R1/R4/R5/R6
U2Pin 1 390DC Pin 9 390DC should be 255+-10%, slightly different values each side - R6 again? also R7/8/9
U3 435 U4 428DC - ????????? what pins??
U1 Pin3 1.59DC Pin 8 1.61DC should be 1.4+-10% - OK within valve tolerances
U2 Pin3 24DC Pin6 24.5 should be 84v+-10% - check R6 as above
U3/U4 Pin8 41DC.

John

Thanks for the reply John its very much appreciated.
Yes it’s a range finding DDM
I checked the IEC earth and the chassis as described in the instructions. Everything else was checked with the earthy lead on the chassis earth as there was no instructions not to, have tried testing everything both ways now and doesn't seem to make a difference
R27 is a 10R and looks fine. If I test the IEC earth and the speaker earth I get 10.2R so is that right?

Sorry U2 Pin 3 is 9.99k so OK

‘Switch your multimeter to show AC volts and check the voltage at the
output of the power transformer across the pink leads to the PS tag board
(26 & 28 ). It should read close to 325v AC.’
To be honest I didn’t understand this either, the instructions state
Not sure how I can check across the two pink leads as well as 26 and 28
Anyway across the two pink leads I am getting around 400AC still higher than the 10% tolerance.

I have checked the all the resisters you suggested and they all seem fine, the only thing I realised I have done differently from the XL version is that I don’t have C9a as I followed the basic version for this. Would adding the C9a make that much difference?

I will check everything again and wait for the reply on C9a but if that’s not the culprit then I may have to find a friendly HIFI shop locally to help as there seems to be too many high and low readings. I am also not getting any light from the LED?

[bob orbell]

What John is saying with regard to the two pink leads and 26 & 28, is that the pink leads terminate at "tag 26 & "tag 28, this is the place to put your test leads with the meter set to AC volts, and the power on, is should read close to 325 volts, for your ref. this is the HT, ac to the rectifier. Be very careful, this voltage will kill. BOB To add, are you testing live voltages with all the valves in? 400 volts at the two pink leads would suggest not, and no light from the LED also suggests not.

[bearded fiddler]

I'm going to rebuild my WD88VA (integrated) with my favourite components (Kiwame, JJ electrolytics, Elna Silmic etc.) and with the XL upgrade.
C9a, C12a and C13a are 1.5uF. I would like to use 2.2uF caps because I have loads of them. C12 and C13 are 220uF/500V, but JJ don’t have them, so I have to choose between 200 and 250uF. Any advice?

Jan

[Richard]

I'm going to rebuild my WD88VA (integrated) with my favourite components (Kiwame, JJ electrolytics, Elna Silmic etc.) and with the XL upgrade.
C9a, C12a and C13a are 1.5uF. I would like to use 2.2uF caps because I have loads of them.

Hi Jan, no problem these are bypass to lower the HF inductance of the combined cap and 1/100 value is a rule of thumb so 2.2uF plastic film will be fine.

C12 and C13 are 220uF/500V, but JJ don’t have them, so I have to choose between 200 and 250uF. Any advice?

It's a ss rectifier which will have no problems so just go for the slightly higher 250uF caps for slightly better smoothing. Indeed the usual 20% tolerance of electro's can overlap in these values anyway

[bearded fiddler]

Thanks Richard! To the point as always.
Jan