Tr-Rack Power Supply question

[superjx10]

Hi all - first post!

Just had a quick look inside the TR Rack - mine is marked with a 117V sticker on the back. Although I live in the UK, it came from US stock. I've been running it using a 240V-120V adaptor for 2 years.

The PSU is marked as KLM-2038A and has a 2A fuse on the PSU board.

First of all I undid the 2 5 way connectors on the PSU board that feed the unit, then plugged it into the 110V supply. I checked these with a multimeter and got:

Green Brown Brown Brown Brown
0V 30V 15V 30V 20V


Orange Red Red Red Red
0V 30V 15V 30V 20V

I then took a deep breath and plugged it into 240V, switched on and off, checked the fuse - no probs.

I switched back on, checked the voltages, all exactly as above.

I switched off, reconnected the 2 connectors, switched back on, and all was fine. 2 hours in and all is still fine.

Conclusion - synthjoe is absolutely right, the KLM-2038A PSU is definitely an auto-switching one.

Looking at the Trinity Service manual (I don't have a TR one), it says that the fuse rating should be 2A for 110V use and 1A for 240V use. I reckon that the fuse fitted in the factory dictates what the sticker on the outside says! I haven't changed mine as I don't have a 1A fuse to hand, but next time I go to Maplins, I'll pick one up.

Dammit, I admitted I've been in Maplins - please don't think ill of me...

So, malmi315 et al in 240V regions, go for it with confidence!

DBP

P.S No Korg TR-Racks were harmed during the writing of this post...

P.P.S Has anyone got a TR-Rack Service Manual?

[synthjoe]

Glad it worked for you too! A couple of remarks and warnings, though:

First of all I undid the 2 5 way connectors on the PSU board that feed the unit, then plugged it into the 110V supply.

You should never test/measure a switching mode power supply (SMPS) without load. It may damage the SMPS, but even in the best case it will work out of spec, just as the voltages you have measured show it (you should have measured +/-15 V and +5 V).

I reckon that the fuse fitted in the factory dictates what the sticker on the outside says!

Well, it is rather the other way around: the supply voltage dictates what fuse rating should be fitted. Since the power used by the unit does not change between regions (:)) for half the voltage you need to supply double the current to get the same power. Simple electricity equation (P=UI).

I haven't changed mine as I don't have a 1A fuse to hand, but next time I go to Maplins, I'll pick one up.

Higher rating works but indeed it is wise to change it to the correct rating. However, I must say that these fuses hardly protect anything related to the circuitry of a SMPS, rather protect against fire and in that sense 2A is hardly any different from 1A. If the SMPS fails then it is just as likely to blow all components with a 1A fuse as it is with a 2A fuse. So, no real need to rush for a replacement fuse, but on the long run it makes sense. On the other hand, when moving from 230V to 117V it might be a necessity to change the fuse - but the TR rack draws 18 Watts only, for which a 1A fuse should still suffice...

Conclusion - synthjoe is absolutely right, the KLM-2038A PSU is definitely an auto-switching one.
...
P.P.S Has anyone got a TR-Rack Service Manual?

Thanks. Sorry, I have no service documentation for the TR rack, I just took it apart and learned by doing it...

[malmi315]

You can download service manual thanks to my friend Rob Senso from here http://www.synfo.nl/

Marcelo

Thanks SuperJX beta tester and Synthjoe. Tomorrow I gonna PLUG !

[synthjoe]

You can download service manual thanks to my friend Rob Senso from here http://www.synfo.nl/

Marcelo

Thanks SuperJX beta tester and Synthjoe. Tomorrow I gonna PLUG !

Greetings to your friend - excellent page and a wealth of service information for lots of great stuff!

Thanks for sharing it!

[superjx10]

Thanks synthjoe and warnings heeded!

My comment on the fuse and voltage was meant to suggest that in the factory, Korg would assign the destination country voltage by means of a sticker and the appropriate fuse - higher voltage, smaller fuse and vice versa - so yes, supply voltage in destination region for export would drive a bill of materials which would include the appropriate fuse and labelling. I was just putting my Manufacturing head on... but reading back, it's kinda gibberish. I promise I'll post more coherently in future!!!

Meanwhile, it's still working... and thanks to malmi for the link.

DBP

[paradox]

hey i know this is old, but is this true?

I am short a step down transformer after getting some new equipment, would i be able to use a standard Aus "kettle cord" to plug the unit in directly to 240v point?

[paradox]

Can confirm this works for TR rack.

[synthjoe]

Glad it worked! Sorry for the late reply - I was offline for the last 8 months or so...

[paradox]

it was a heart stopping moment, but it works haha. cheers synthjoe!