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AKAI GX-210D first power on in 13 years = unlucky burning smell.

A

AudioAu

New Member
Hi,

from power on after all that time things seemed to be going well until loading a new tape resulted in a mechanical stuttering sound (motor?) followed by electronics burning smell. I switched off before anything went bang and will get to inspect closer in coming days.

From my reading and review of the circuit diagram it seems that Capacitor C1 Part No. EC350987, Description MP 0.47uF(M) 250VAC could be to blame.

I'm interested to hear the opinion of others and if in agreement with that component diagnosis whether this modern day part is suitable as a replacement:

https://au.element14.com/kemet/pme271m647kr30/cap-0-47-f-10-paper-radial/dp/9717501?st=mp capacitor

John
 
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Closer investigation has revealed burnt Resistor 8-R6 (Carbon RD1/4 100(J). From its visual appearance (bright/clean) and the fact it still measures correctly as 100ohms I'd say it's just happened. Could rotating the reels by hand to load the tape while paused cause this?

Components connected directly or in immediate proximity tested as follows:

8-D1 Silicon Diode 10D4 - Multimeter Diode checks correctly in circuit.
8-C1 MP 0.47uF(M) 250VAC measures 0.63uF out of circuit which equates to 34% higher than labelled using a Peak LCR40 passive component analyser.
8-C2,3 Elect. 47uF 160WV - Measure as 76 and 72 uF out of circuit being 61% and 52% higher than labelled using a Peak LCR40 passive component analyser.
8-R1-R4 Wirewound Cement resistors all measure correctly out of circuit.

So with all that said I'm resisting just changing the burnt resistor as something must have caused it.
The capacitors measured above while higher than labelled value are from what I'm reading still in spec for surge buffering and smoothing applications or are they more critical here?
Do I need to check the spark quenchers also?

Thanks in advance for any help offered.

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Greetings from RojoLand!

Replace that burnt 100-ohm resistor, and both C2 and C3 (their higher measured value suggests they are leaky). Use 47 µF, 200 V (or greater), 105°C electrolytics. The capacitor you specified to replace C1 seems fine to me. Should you change out the spark quenchers? Measure them out-of-circuit for DC leakage; any that show resistance should be replaced (and if you find more than two bad ones, do all six).

The 10D4 diode can be replaced with a 1N5408 (or UF3008) if needed (both are 3 A ,1000 PIV diodes, perhaps overkill). It may have checked OKeh on your tester (likely a low-voltage test), but this circuit operates with around 100 VAC at terminal A of that PC board and the diode *could* be breaking down at the higher voltage.

Take care,
—
J. E. Knox "The Victor Freak"
 
AudioAu said:
How did you arrive at 1N5408?
Click to expand...
Rojoknox probably recommended this diode instead of the 1N5404 or 1N5406 since it provided greater safety margin with minimal cost difference.
AudioAu said:
My research had led me to the 1n5404 and 1n5406 which are obtainable here although I'm unable to find mention of "non-Repetitive Peak Reverse Voltage" to be absolutely sure of the substitution.
Click to expand...
This is not likely to be an issue since the Maximum Repetitive Peak Reverse Voltage rating of the 1N5408 exceeds the Non-Repetitive Peak Reverse Voltage rating of the 10D4.
 
Last edited:
Ok understood. For my own education I'd still like to be able to identify the most minimum or most equal equivalent so is that the 1n5404 or 1n5406?

thanks
 
The specification sheets for the the 10D4, 1N5404 and 1N5406 show the following:

10D4 - If(AV) (maximum average forward current) 1.5A, VRRM (maximum repetitive peak reverse voltage) 400V
1N5404 - If(AV) (maximum average forward current) 3A, VRRM (maximum repetitive peak reverse voltage) 400V
1N5406 - If(AV) (maximum average forward current) 3A, VRRM (maximum repetitive peak reverse voltage) 600V

Based on this, the 1N5404 is the one that most closely matches the specifications of the 10D4, however this does not mean it is the best choice as a replacement.
 
Ok, good news bad news story.

The good news is that after fitting the replacement parts everything worked as it should and I've been listening to music for hours :-)

The bad news is that I've just heard some squealing sounds during playback and then the motors slowed to a stop. Fast Forward and Rewind are hesitant to start but when they do it doesn't take long for them to slow to a stop.
Both motors seem to move freely by hand but I have no point of reference to know if they are stiff or not.
I'll offer this as a clue but maybe unrelated, during playback there was an ever increasing smell of warm old electronics (dust, flux) that I recognised from valve radios but not an electronics burning smell as in frying/failing components.

So given its very light use prior to being stored 13 years ago I'm not expecting anything to be worn out so is this simply a lubrication issue and if so where should I start?
 
An extra bit of info now that I've let it cool down.

With the tape loaded (not playing) and the take up reel wound backwards a little to take the pressure off the right hand side tensioner it all sits there quietly. If I manually rotate the take up reel so that the tensioner just starts to lift to mid way through its travel a chattering sounds starts that only stops when the tensior is lowered again.

I remember this sound from the first failure resulting in the resister smoke.
 
Capstans should be removed, cleaned and lubed with sewing machine oil or synthetic motor oil at the minimum. All these old machines NEED to be disassembled and lubricated properly. Think of a car sitting in a garage for 30 years. Anything rubber will most likely be hard as rock(idler tire). Anything that had oil will be dried up (Capstans). Any grease will be hard/sticky(transport,pinch roller arms etc)
 
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