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Author Topic: Ami Rowe CD100 pre-amp issue  (Read 2893 times)

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jimbob

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Ami Rowe CD100 pre-amp issue
« on: October 14, 2019, 09:41:45 am »
Hi,


I have a Rowe Ami CD 100 - I've have it for 15 years & it worked well when last used around 5 years ago. I'm now trying to resurrect it.
I have no sound, and following the testing steps in the manual I believe the pre-amp is dead.
I know the CD mech is working fine & outputting sound (plugged that in to an amp and it works fine).
I've tested the pre-amp thus:
disconnected the "Mute" plug and lead to output tx.
shorted out all 5 pins of volume control.
verified that I have up to 0.2V rms at the line in from the CD (at the solder joints for the phono connector)
Measured at the pre-amp output (pins 3 & 5 of 13 pin connector) there is no AC voltage (ought to be 1V ish according to manual)
Board is dated 1989,
1st question - is there anything I could be doing wrong in my testing (I do hope it's that!)
next -
 is there any further testing to further isolate the fault?
are there common component failures on these?
(I'm handy with a soldering iron, so I'd be up for repairing it)

If that's a dead end, is there anywhere I can get a replacement in the UK? (there do seem to be some from the US on ebay)

Or... (sacrilege I know) does anyone have advice on swapping this pre-amp for a non Ami Rowe alternative?

Looking forward to any tips anyone has!

Best,

James

Ken Layton

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Re: Ami Rowe CD100 pre-amp issue
« Reply #1 on: October 14, 2019, 09:54:02 pm »
Considering the age of the jukebox, I usually re-cap the preamp board and the two driver boards in the amplifier. Several small value electrolytics on the preamp board go bad. They are usually the ones next to the heat sink of the voltage regulators.

jimbob

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Re: Ami Rowe CD100 pre-amp issue
« Reply #2 on: October 18, 2019, 01:10:10 pm »
Hi Ken,

Thanks for the sugestion - I've tried unsoldering the 2 caps that looked the most at risk - both tested completely fine on my DVM....
Do you think it's really worth me replacing all the electrolytics on the board? There are lots! Clearly, if I was sure that it would fix it I'd crack on, but given the fact that both channels are just completely dead, I just have this suspicion that I'm missing something stupid, something in the power supply maybe, though there seems to be +39v and -39v coming up from the main amp boards....

Cheers,

James

Ken Layton

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Re: Ami Rowe CD100 pre-amp issue
« Reply #3 on: October 18, 2019, 11:15:32 pm »
I use an "ESR" reading capacitor meter to check the electrolytics.

Also, check for bad solder joints at all the connectors on the boards.

I'm assuming you have the preamp jumper plug installed on the amplifier and that's it's connected in the correct orientation (NOT plugged in backwards which is easy to do).

ami-man

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Re: Ami Rowe CD100 pre-amp issue
« Reply #4 on: October 21, 2019, 07:50:13 am »
Hello James,

I am based in the UK and undertake repairs on Rowe Ami amplifiers.
If you wish to send me your amplifier for testing/repair please send me a PM.

Regards
Alan

Alan Hood
ami-man
UK

jimbob

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Re: Ami Rowe CD100 pre-amp issue
« Reply #5 on: October 21, 2019, 10:58:07 am »
Alan- I might just do that...

Ken,
I do have the 13 pin plug in place, I'm pretty sure it's the right way round (1 to 3, 2 to 7, 5 to 9, 6 to 8)
I've also shorted all the pins of the volume control as directed by the manual

I've tried following the signal from the RCA socket, where I have around 0.1 to 0.4V AC.
I've guessed that it's heading to the closest op-amp - a 4558CP.
the weird thing about that is it would appear that supply voltage for that and all the other similar op amps is 2.6V, which seems too low....

I don't suppose anyone has a schematc for the pre-amp?

best,

James

Ken Layton

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Re: Ami Rowe CD100 pre-amp issue
« Reply #6 on: October 21, 2019, 12:28:43 pm »
Preamp schematics and board layout/parts list are in the manuals set.

jimbob

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Re: Ami Rowe CD100 pre-amp issue
« Reply #7 on: October 21, 2019, 04:17:33 pm »
Thanks Ken - I overlooked that - I thought I'd printed out all the useful bits, but I missed that page!

jimbob

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Re: Ami Rowe CD100 pre-amp issue
« Reply #8 on: October 22, 2019, 04:26:15 pm »
Hi Ken,

The schematics were very helpful - it helped me chase down that the +/- 15v supplies were suspicious.
I've taken the LM317 and LM337 out. One is def. cooked, the other may be OK.
I hooked them up on some breadboard.
the LM317 gives no output voltage.
the LM337 gives a voltage close to the input voltage and that varies with Vin.
I'm going to start by replacing these....


J
« Last Edit: October 22, 2019, 04:44:41 pm by jimbob »

jimbob

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Re: Ami Rowe CD100 pre-amp issue
« Reply #9 on: October 29, 2019, 07:43:35 am »
A quick update in case it helps others.

I replaced the LM 317 and LM337, the power supply to the pre-amp was restored and I'm back up & running - it all works!!

I've no idea what blew them, and how long they'll last, but I'm fixed.

So to anyone who encounters pre-amp failure, check your +15v and -15v lines, and if they're not the correct voltage try swapping the regulators.

Thanks to Ken for your help!

James


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Re: Ami Rowe CD100 pre-amp issue
« Reply #10 on: October 29, 2019, 11:50:37 am »
Glad you got it running. :)