ecc83 ecc83 ecc82 - madcogz.com
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EL34EL34EL34 EL34
ECC83 ECC83 ECC82
ECC81
CCT board is green on track side but brown on componant side �
Looks like V125 BASS
(Cct board has no FETs in input stage
but some differences:
Both inputs are wired together and present a single input to the V1 (pin 7).
Amp has a dual ganged distortion control (not sensitivity like in either V125 LEAD or V125 BASS).
Output to speakers is switch selectable (not like V125LEAD)
Has 2 x signal diodes (after V2 ?) not in V125 LEAD cct�
INPUTS
2 x signal diodes
(back-to-back to
chassis)
DIST VOL
HUM Balance
between heater
bus’s
BIAS
MAST
Climax
REPLACED
And all tubes even though 2 x EL34 were
OK and the ECC8x’s seemed OK
EL34 V5
EL34 V6
EL34 V7
EL34 V8
1
4
5
3
8
ECC81
V4
ECC83
V2
ECC82
V3
mains
Output
transformer
C27a
C27b
INPUTS
Does not match V125 Lead, or
V125 Bass schematics.
Looks more like AC120
pair
pair
History:
Purchased 2nd hand about 1987
Initial issues :
Fine for a few years then developed a trait of after an hours
usage, the volume would start to waver and drop, and then all hell
would break loose.
Relegated to the storeroom...
UNTIL NOW !
Current issues:
HT fuse blew at power on
2 / 4 output tubes look cloudy
Broken CAP in EQ
Broken EL34 during testing
Lots of dry joints
Current notes during testing
Loud hum and much (microphonic) crackling.
Resoldered many dry joints
Replaced all tubes
Replaced all caps in EQ
Replaced several ‘darkened’ resistors
Replaced broken greencap
.
blackPink
grey
Grey/
black
Blue tap
RED tap
White tap
SPKR SPKR
150K
150K
1M5
10nF
ECC83
V11 6
2 7
83
BRILLIANT
NORMAL
INPUT and
OUTPUT wiring
OUTPUT
INPUT
TBC:
but looks more like an
AC120 input channel
Does not match V125
Lead or V125 Bass
schematics.
Look
Familiar ??
AC120
My V125
inputs
Credit: Phydauex for sharing the TAP colors and impedances : http://music-electronics-forum.com/t24513/
(red/pink=8 ohm tap, white=4 ohm tap, blue= ohm tap/earth, grey wires=internal speaker)
black
PINKgrey
Grey/
black
Blue tap
RED tap
White tap
Speaker switch witing
This is how mine is wired8
I don’t know for sure if this is
correct.. .it’s just how it is 8.
OR
AND
ECC83
V116
27
8 3
150K
150K
1M5
10nF
DIST
Pot-2
47K LIN
8
7
6
3
2
1
(ECC81)
Found to be
47n
Replaced with
100n
470n
ceram
3
2
1
(ECC83)
(ECC83)
3
2
1
8
7
6
(ECC82)
4k7
4.7uF
4.7uF
All 4 EL34 :
100K + 10K via pin 6
(see side diag.)
56n
10K
100K
Do these (plate) voltages
need to be swapped too
???
8
7
6
None of this part matches what
is actually in my amp.
DIST
Pot-2
47K LIN
(dual gang)
8
7
6
3
2
1
(ECC81)
Found to be
47n
Replaced with
100n
470n
ceram
3
2
1
(ECC83)
(ECC83)
3
2
1
8
7
6
(ECC82)
4k7
4.7uF
4.7uF
All 4 EL34 :
100K + 10K via pin 6
(see side diag.)
56n
10K
100K
220k
100k
220k
100k
47k
47k
3
2
1V1
2k2
2.2n
DIST
Pot 1
47K
LIN
(dual-gang)
100k
2.2n8
7
6V1
2.2n
2k2
2 x 1N4184
150K
150K
1M
5
10nF
100k
100k
? Tbc ?
This may not be correct, but it’s pretty
close as far as I can trace on the cct
board in my V125
(In other words, I’m not entirely sure I
mapped this out correctly)
(ECC83)
(ECC83)
8
7
6V2
4k750n
R14
100k
220k
100k
220k
100k
47k47k
3
2
1V1
2k2
2.2n
Dist
Pot 1
47K
LIN
100k
2.2n8
7
6V1
2.2n
2k2
2 x 1N4184
150K
150
K1
M5
10nF
100k
8
7
6V3
100k
R16
100k
22k
1W
R31
1K 1W
R32
100R 5W
R33
stndby
47K
R29
C27b
32uF
C27a
32uF
56K
R28
V4-P1
V4-P6
485v 430v
405v
275v
280v
8
7
6V2
4k750n
R14
100k
220k
100k
220k
100k
47k47k
3
2
1V1
2k2
2.2n
Dist
Pot 1
47K
LIN
100k
2.2n8
7
6V1
2.2n
2k2
2 x 1N4184
150K
15
0K
1M
5
10nF
100k
8
7
6V3
100k
R16
100k
22k
1W
R31
1K 1W
R32
100R 5W
R33
stndby
47K
R29
C27b
32uF
C27a
32uF
56K
R28
V4-P1
V4-P6
485v 430v
405v
275v
280v
Rear of input jacks (red wire goes to ECC83 (V1 ?)
Pair 1 Circuitry OK
(not blowing HT fuse or valves)
Pair 2 Circuitry OK
(not blowing HT fuse or valves)
CAP is clearly broken � and
what is going on ith that furry
trim-pot ???
VOX V62.5 ???
Climax
150K
150K
1M5
10nF
ECC83
V11 6
2 7
83
ECC83
V21 6
2 7
83
ECC83
V116
27
8 3
150K
150K
1M5
10nF