Rowe Ami R-83 Replaced DS1 & 2 and still low audio output

[radioman]

Hello to all!
For those interested first the correct number for the two submini bulbs used on the pre-amp board for the R-83 Amp is 1764. I had no trouble finding replacements at our local electronics shop.

Replaced both as each had a broken lead to the pcb and thought wow this should do the trick.......Well it did not.
I pulled all of the Darlington outputs out of the heat sink and all read good and about the same. All solder joints are fine, and from what I can tell everything else checks out good but still just faint low audio. This one is realy trying my patience to say the least.

I had the box running for about an hour last night and the heat sink does not appear to be getting warm which could be a clue?

We have a party set for next weekend and really wanted the machine up and running again for all to enjoy but running out of ideas!

If anyone can shed some light on this for me it will be appreciated.

Thanks!
Rich

[ami-man]

Hello Rich,

Do you have a dual beam scope and a single generator? if so put the scope on the two outputs from the amp. and put the signal generator on the jumper plug connections
1 to 3 and 5 to 8 to make sure you have an output from the two driver boards.

If that is ok move the gererator onto the input and test again. The pre-amp gets it power from the driver boards.

You can put the scope on the jumper plug connections just to test the pre amp.

Regards
Alan

Alan Hood
ami-man
UK

[radioman]

Alan,
Thanks!
Scope yes generator no so I will do the best I can to try to trace the circuit. I thought for sure when ds 1 & 2 were broken I may have found the fault but no such luck. I think this may have taken a surge a while back as it had a blown 27 volt diode light in the power supply which I repaired and also changed the voltage regulator and drive transistor just as a precaution while I had the supply apart. It was an easy fix.

To make matters worse Sunday afternoon in my game room I was watching my Toshiba big screen tv and half way through the NASCAR Race I lost the video....LOL when it rains it pours. I now have it apart and hope to fix this later today and get back on the box as again we have a big party on Saturday and now no Tele or Music...Bummer!
Thanks I hope I can find a solution as you can work the juke but the sound seems like just pre-amp audio at a low volume and wont be much fun for the guests.

BTW Can I take signal or pre amp audio out of the box and run it through an external amp as a temporary cure to use the machine this weekend?
Me and my friend who owns the local tele repair shop were wondering if we could just use it like a turntable??

Many Thanks!
Rich

[ami-man]

Hello Rich,

Of course you can set up a temp amp and use extension speakers for your party.
The Shure 44 series cartridge which should be the cartridge fitted, will give an output of 6 to 9 mv.

In my last post I mentioned the jumper plug that connects the input (pre-amp) to the output stages (driver boards) is this fitted and fitted the correct way round?

You have links on the jumper plug of 1 - 3, 5 - 9 and 6 - 8. Link 1 to 3 is towards the amplifier handle.

Make up a test volume control, to go direct to the volume connector on the amp, use a 10k log pot one side of the pot to pins 1 & 5 (linked) of the volume plug and the wiper to pin 3 (normally there is not a wire to here it is picked up via the other wiring but the ground is required to control the volume).
You can also pull the mute plug out to see if you have a mute issue.

Please let me know how you get on.

Regards
Alan

Alan Hood
ami-man
UK


 

[radioman]

Alan,
I am sorry I did not get back to you but we had the large gathering Saturday and Sunday with about 100 plus people from the Oldsmobile Club of America and all my time ran out before. I did not get a chance to "Hot wire it" to an amp and now will have some time to trace back and see just what the real problem is.

It is very frustrating and Bruce does not do repairs on this model amp so I am off on my own  quote with a little help from my friends...LOL
Thanks!
Rich

[ami-man]

Hello Rich,

OK haver you got a hi-fi separate CD or tape player, what we are looking for is an output of around 500 to 600mv. Connect the phono output from the CD or tape to the connections on the jumper plug on the amp to pin 1-3 and 5-8. o get it to play unplug the mute plug or sellect a record and lift the arm whilst testing.
If you get a reasonable output of sound the fault is on the pre-amp.

If this is the case you can send me the pre-amp to test/repair, alternatively you can send the amp to Ron Rich who is a fellow moderator on the PhonoLand forum.

Regards
Alan

Alan Hood
ami-man
UK