[marcspace]

Hi guys,

I switch on the lunchbox, the resistor R31 get burned, please help.

R31=5.3 ohm (normaly 5R6)

Thnx

[JPK]

Make sure you didn't swap U3 (THAT1512) with U4(THAT1646).
Is is the same without the tube plugged in?
Look for solder bridges, reversed diode, transistor or IC.

[marcspace]

 problem solved,

U3 and U4 swapped!!!


You're the GOAT!!!


thnx

PS: R31 5.3 ohm is fine? better to change it?

[marcspace]

Problem test:

all tests passed, Voltage are fine, but 

DI Preamp Check (when I press the button preamp and increase the knob, no I've sound)
DIST Check (the same way, when I press the tube knob the sound leave)


Thnk in advance

[JPK]

You have probably destroyed the THAT1646 when swapped.

[marcspace]

Hi JKP,

I've changed U3 and U4, now pre amp work fine, but when I push the DIST Botton in tube mode, the sound leaves.



THAKS IN ADVANCE

[marcspace]

Hi JPK,

H=5.6V
HT=46.5V
V+=15.6V
V-=15.5V
TP1=0V
TP2=25.6 V
TP3=0V


Thnx

Mark

[JPK]

Check components value and solder joints of C9...C11, R17...R19, L1, TR1, J3, J4, SW3.

[marcspace]

All measurements of the capacitors and resistors, such as the soldering, are fine, the switch commute., trimmer goes to 0- 50 k.

The only component I cannot measure is L1. (don't have the measuring tool for microhenries)

Thxs

[JPK]

You can check the DC resistor which is about 160 ohms.
You can try to follow the signal with an AC voltmeter:
on TP2, R16 top, R17 down, R17 top, R18 down, R19 top, J3 pin1 (square pad).

[marcspace]

Hi JPK,

I found the problem it's L1 (no measurement mH, I've bought the tool;))


Thxs for all


Mark