Aoyue 738 4 in 1 solder station power board

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

Hi mate
Not quite sure where the 5v circuit starts and ends
was going to see if the front panel gets any power by testing the plug cant realy test on the board in situe
Where would the best ground point to test from Com
Thanks for all your time

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

hey mate
i put a 5 watt in there all i could get in the middle of rural Western Australia

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

I measured the voltage while powered from five pin header by the large Atmel from left hand pin of left hand resistor
from left to right on power board
1 2.129v
2 2.883v
3 2.137v
4 2.095v
5 2.047v

front pannel 5 pin header opposite right to left
1 2.128v
2 2.812v
3 2.133v
4 2.101v
5 2.099v

if any of that means anything
but it does mean theres power to the front board so why no disply
has the front board been hit too
Thanks all

[stj]

Re: Aoyue 738 4 in 1 solder station power board

the atmel needs 5v,
if it's an avr then 5v is on pin10, and ground on 11 and 31 but the crystal would be on 12 & 13.
so i dont think it's an avr

so it's probably an 89s51 series.
5v on pin 40, ground on 20 and the crystal on 18 and 19.

and i reduced it to that chip just from the crystal location - proving it's pointless grinding numbers off

[redwire]

Re: Aoyue 738 4 in 1 solder station power board

The 5V regulator is a 7805, so a convenient common (ground) for measurements is the heatsink/tab.
If the 5V is low due to an overload, it will get hot.
I wonder if the hot air heating element touched the thermocouple when it all went down. That would kill an op-amp IC.
Point is, if the vreg is hot then another semiconductor will be as well and it is likely pooched.

[stj]

Re: Aoyue 738 4 in 1 solder station power board

looking at the pictures in the original post,
R7 is almost gone - blown away!
it's under and left of the optocouplers

[redwire]

Re: Aoyue 738 4 in 1 solder station power board

R7 is the opto LED resistor, driven by Q1, for the triac to the upper left of it. Like R5/Q2 is for the triac to the upper right. But R7 looks not blown, maybe a bit baked?

If it is cooked then the opto-isolator should be checked for shorts.
It is normal to see low resistance <100R between the output pins (in-circuit) going to the triac gate, but not between sides.

Somewhere there is a thermocouple input resistor that could have gotten cooked. The whole section around trimpots W1, W2 is for the TC amplifier it looks like. That is what the long traces running under the opto's from J1, J5 are bringing in.
So R24 looks a bit cooked? but the pictures need to be better quality less fuzz and more light. I have no idea how the GX connector makes it to the board.

[stj]

Re: Aoyue 738 4 in 1 solder station power board

the whole board needs a good IPA scrub!

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board





I have cleaned up and retouched solder but i think looking at it i bridged 3 connections by atmel 11 12

I couldnt get to the regulator or the atmel to measure it's at the bottom very tight but ile have another go tomorrow.
I i did put my finger on all the heatsinks and they didn't feel hot.
but it wasn't on for long thou but all values given were high values they all went up and down to 1.3v for equally as long
cheers

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

Dont know what happened with the attachment

[redwire]

Re: Aoyue 738 4 in 1 solder station power board

For the low voltage DC power supply, J4 yellow wires from the power transformer go to 4-diodes for a bridge rectifier that feed C1 and the 5V regulator input. It looks like mostly your standard fare.
The only thing odd is the huge diode and solder bodge looks like it might be a zener or TVS? - if you find the input voltage too low then suspect that big diode.

But the 5V output being low and fluctuating - you'll have to take some more readings.

To troubleshoot the 5V power rail, you don't need all the mains stuff connected to the board, only J4. This is assuming the power tranny has power, I'm not sure how it is wired or the on/off switch etc. It would be less stressful and a bit safer.

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

Hi all
today i replaced the voltage regulator i get 5 volts from the output
Still no display
Any ideas
Cheers

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

The other parts will need sourcing from internet i think

[stj]

Re: Aoyue 738 4 in 1 solder station power board

check that you have 5v at the atmel and display

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

Hi mate
I do get5v at the atmel vcc and a couple of other legs
I get 5v going to the front panel
What shall i try next
cheers

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

And 1 of the big resistors the 2watt gets really hot

[stj]

Re: Aoyue 738 4 in 1 solder station power board

can you identify where the resistor connects?

[redwire]

Re: Aoyue 738 4 in 1 solder station power board

Which resistor?

Two of the three are snubbers with the blue capacitors. The one at the top is in parallel with whatever goes to the two-pin header J2, maybe the air pump coil? I think it's normal to get hot if the air is on full blast or the coil is disconnected.

How does the display connect to this main board anyway? It might be working but the display is dead? It seems to be serial data on J3.

I put coloured felt pen markings on the connectors so I don't mix them up or put them on backwards.

[mentholflash]

Re: Aoyue 738 4 in 1 solder station power board

It was this 1



The display is the five pin header @ the Atmel
Cheers

[redwire]

Re: Aoyue 738 4 in 1 solder station power board

Yes that's the one resistor connected at J2, across or in series with a load? Is that the air pump?
edit: I can't see any problem with that output causing a display problem though. I wonder if the MCU is still alive.