Hi, I recently acquired an Arcam Alpha 3 integrated amp accompanied by matching FM Stereo Tuner. Both units were specified for UK 240V operation and I need to convert them for US 120V. It was easy enough to convert the integrated amp from 240V to 120V operation, since it has split transformer windings and is designed for this conversion.
However from inspecting the PCB it appears the FM Stereo Tuner will need a replacement transformer to convert from 240V to 120V power. Unfortunately I can't locate schematics or the service manual, so don't know what voltage is expected at the transformer secondary. Does anyone have this information handy?
Otherwise is this a valid workflow?
1. Pull the transformer, plug the primary into 120V and measure the AC voltage V at the secondary
2. Order a replacement tranformer rated to produce 2*V with a "reasonable" power rating
However from inspecting the PCB it appears the FM Stereo Tuner will need a replacement transformer to convert from 240V to 120V power. Unfortunately I can't locate schematics or the service manual, so don't know what voltage is expected at the transformer secondary. Does anyone have this information handy?
Otherwise is this a valid workflow?
1. Pull the transformer, plug the primary into 120V and measure the AC voltage V at the secondary
2. Order a replacement tranformer rated to produce 2*V with a "reasonable" power rating
I have the Alpha3 amplifier as well I use it on one of my PC,s for audio , its got a noisy potentiometer but I cant be bothered changing it --watch out for "melting feet " as mine are melting into a black gunge
otherwise it sounds quite nice .
I am looking at- change voltage alpha 3 --you have to cut the TRACK on the short track with a connection at each end and add links from each cut track to the tracks above and below it.
Change fuses to 250ma anti surge for 115V.
otherwise it sounds quite nice .
I am looking at- change voltage alpha 3 --you have to cut the TRACK on the short track with a connection at each end and add links from each cut track to the tracks above and below it.
Change fuses to 250ma anti surge for 115V.
Thank you for all the responses!
@MAAC0 Good point, yes I see a single LM340T12/7812 regulator and a single LM340T5/7805 device. Since there's only one bridge rectifier circuit visible I guess the transformer has a single secondary winding and that it needs to provide a signal to the 7812 device, so as you say I just need to look for a 15-18v transformer!
@adason The model has the same name as the amp. It says on the front "Alpha 3 FM Stereo Tuner".
@duncan2 Thanks for your comment on the Alpha3 amp. The instructions you are referring to are for the Alpha 1 and Alpha 2 integrated amp and don't apply to the Alpha 3 integrated amp (which doesn't require cutting tracks) nor the FM Tuner (which seems to require a transformer replacement).
@MAAC0 Good point, yes I see a single LM340T12/7812 regulator and a single LM340T5/7805 device. Since there's only one bridge rectifier circuit visible I guess the transformer has a single secondary winding and that it needs to provide a signal to the 7812 device, so as you say I just need to look for a 15-18v transformer!
@adason The model has the same name as the amp. It says on the front "Alpha 3 FM Stereo Tuner".
@duncan2 Thanks for your comment on the Alpha3 amp. The instructions you are referring to are for the Alpha 1 and Alpha 2 integrated amp and don't apply to the Alpha 3 integrated amp (which doesn't require cutting tracks) nor the FM Tuner (which seems to require a transformer replacement).
Post detailed photos of the innards especially the multiplex section. You need to figure out how to change the de-emphasis from 50usec (European) to 75usec (North American).
Measure the actual AC secondary and measure the current draw. You don’t want too much power dissipation on the existing IC regulators. Picking an 18V over a 15V or 16V secondary is likely going to double the 7812 power dissipation.
Measure the actual AC secondary and measure the current draw. You don’t want too much power dissipation on the existing IC regulators. Picking an 18V over a 15V or 16V secondary is likely going to double the 7812 power dissipation.
Well that's funny Ralph as it actually names the Alpha3 as applying to it and the D280
Tuner not the amplifier
If the upload doesn't work then-
ARCAM D280 ALPHA3 ALPHA5 TUNER SM Service Manual download, schematics, eeprom, repair info for electronics experts
If the upload doesn't work then-
ARCAM D280 ALPHA3 ALPHA5 TUNER SM Service Manual download, schematics, eeprom, repair info for electronics experts
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@duncan2 my apologies! I was thinking of the "CHANGE OF MAINS VOLTAGE (ALPHA)" section of the Amplifier service manual available here: https://www.hifiengine.com/manual_li.../alpha-3.shtml
Thank you so much for sharing the Tuner service manual. I see now that I don't need to buy a new transformer but just need to cut and add links to the PCB in the area shown in the attached image.
While not explicitly mentioned I guess I don't need to change the fuse but I do need to follow the steps in the service manual to change capacitors for US deemphasis standard (as @ej25awd also mentioned).
Thanks again
Thank you so much for sharing the Tuner service manual. I see now that I don't need to buy a new transformer but just need to cut and add links to the PCB in the area shown in the attached image.
While not explicitly mentioned I guess I don't need to change the fuse but I do need to follow the steps in the service manual to change capacitors for US deemphasis standard (as @ej25awd also mentioned).
Thanks again
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While not explicitly mentioned I guess I don't need to change the fuse but I do need to follow the steps in the service manual to change capacitors for US deemphasis standard (as @ej25awd also mentioned).
Thanks again
Thanks to duncan2 for the SM link! I missed that.
Yeah so to change the de-emphasis, remove the ‘B’ jumper link and add an ‘A’ jumper link. This will change the total capacitance in parallel with 68k from 690p to 1n03 which in turn will change the RC time constant (the dominant de-emphasis network) from 46usec to 70usec.
Unless I'm misreading the SM, the jumper-based deemphasis change only applies to the Alpha 5 tuner, and for the Alpha 3 model you have to replace two 220pF caps with 560pF ones (looks like these items on ebay).
Here's the two caps C42 and C43 that need to be replaced for US deemphasis convention on the Alpha 3 tuner. They read "220pJ 63- EVOX PFR".
And you're right it looks like something like this from Mouser should work: PFR5561F63J11L4BULK KEMET | Mouser
And you're right it looks like something like this from Mouser should work: PFR5561F63J11L4BULK KEMET | Mouser
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