[Die_Bogener]

There are some resistors in the power supply as “fuseable resistors”…

They just burn out… sometimes difficult to see.

[alf]

Hi All,

sorry about that rather vague description of the issue at hand.

i had to repair the power supply as a short killed two(?) of its transistors.

the supply voltages are there but the deck does not turn on. It started off with the display lighting up for a moment only, now there is nothing.

I replaced some capacitors on board #2 and tested various transistors on that board….still nothing, no adverse findings.

of course the tape drive does not engage nor is it getting the 12VDC which seem to disappear on the way from the power supply.

both coils of the solenoids of the tape drive show about 27 Ohm. After having spent

hours and hours to find any culprits it seems like the stage of parting out has been reached ?!

its a shame as the deck is in very nice condition and performed .

are there any pointers from someone in the know ??

ALF

[alf]

Thank you for the pointers – I thought I did check but will revisit the PSU section.

It seems odd though I can measure the 5VDC, 15VDC and 26VDC supplies on P2 & P3

ALf

[solderon29]

Hello Klaus,you get some interesting problems?

This machine has a “safety circuit”,designed to stop it functioning if anything stops the mechanism.I imagine that the capstan belt has perished by now,and the mech is jammed?

The computer monitors the consumption of the capstan motor,and shuts the machine down if it becomes excessive.

Could it be that?

Nice machine of course-good performer.

Nick

[alf]

I did get back to follow up your suggestion:

all resistors on the PSU section have been tested and all tested ok.

to my understanding the PSU section supplies the necessary voltages to board #2 but

the display is still dead, the drawer motor does not engage nor does the tape drive although when the mains is switched on I can hear a short click in the drive , as it would try to engage ?…..that’s it.

I feel the 4.6VDC is not enough to light up the display and it puzzles me why and where the lack of voltage is happening ?

will get over it once more – not overly optimistic about a good outcome though.

ALF

 

 

[alf]

Thank you Die and Nick for your inputs – this is where I am at:

i checked 2TR17 which is fed with a 5 VDC supply which tested ok – then checked TR3 on the display board which tested ok.

suddenly the drawer motor came back on board and so did the display…..seems totally unrelated to me but…no complains.

then I checked the belt was fitted correctly and not running on the edge of the black flywheel – belt was sitting perfectly….and NO, the belt is fairly new.

and again: when play is activated the display comes on for a moment, I can hear what has to be the clicking of the solenoides of the tape drive but it just wont play !!

When unsoldering 2P16 I lost the soldering eye of pin1 which is connected to ground – so is Pin5. In that case I connected those two pins. (I blame the desoldering gun)

looks like I still have to find the cause of the not firing tape drive.
One thought was on those two grey wires which connect to the capstan motor terminals A and B.

obviously there were two options of making the connection, so I tries both without any impact on the issue at hand.

any help is most appreciated – thank you

ALF

 

[alf]

Hi All,

just a quick update:

I have the 15.5VDC at 2R172 and 14.9VDC at 2R171 but I can not see the 12VDC at the crosspoint of emitter of 2TR38 and collector of 2TR37.

i checked TR37 and installed a jumper from C of 2TR37 to P16-4 thanks to a broken track.

But there are still no 12VDC at 2P16-4, hence no supply of 12VDC for the capstan motor ??

at the moment I am turning in circles….progress but no progress ?

any comments or pointers ?

ALF

 

 

[Die_Bogener]

Use a seperate regulated and controlled digital power supply.

Then you see, wether there is a broken line, dead transistor or overload… the additional power supply and its adjustment will decide wether it does something or there are smoke, glowing parts or funny crackling lines.

[alf]

Hi All,

here’s an update:

2 broken tracks were enough not to supply the tape drive – it is now operating.

that was a big step forward. The next issue is the display (logic issue?) and full stop.

the display comes on for a moment but goes back off while the tape is still running after play is initiated.

when the tape comes to the end (stop) the capstan is still running, meaning the deck does not completely shuts off.

Does the reset on 2IC8 happens automatically or is there a procedure to initiate a reset on IC8 ?
there is a reset section on the circuit diagram.

The other question is : does the deck have a logic problem that causes the issue?

no, I can do without any further fireworks or smoke ?

ALF

 

[alf]

Further up-date, although nothing entirely new:

i have revisited the display – all voltages are present but the 22VDC are actually 24.6VDC which may be too high ?!

the display still comes on for a moment but goes dark again – the supply voltages don’t seem go break down which puzzles me.

the capstan definitely keeps running unless I switch off the mains voltage.
I can not imagine that it spins in St-By mode.

there much be a kind of timer after the deck goes back into St-By mode ???
i did run the tape briefly after disconnecting the protection input to 2IC9 but it made no difference towards the remaining issues.

the issues at hand must be related to the control section.

it looks like a Martin intervention is urgently needed to get to the end – i am running out of ideas how to proceed.

ALF

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