Rockola 1458 makes wrong / multiple selections

Dear juke lovers!
I am Rudolf from the Netherlands. A short bit of history: many years ago I bought an Ami H200E and fully restored it. Had it for 15 years playing in the livingroom. About six years ago I thought is was time for something else, so traded the Ami for a V200.
I love working on the old machines so much and the V200 had been trouble free for many years now. So last winter I bought this Rockola 1458 and I'm onto full restoration.

So my problem:
The 120 selection system is divided in 3 divisions: BLUE, YELLOW and RED (3x 40 selections)
When I select Blue#1 then also Yellow#1 and Red#1 gets selected. This happens with multiple numbers. So for example #21 does the same.
I checked and only the correct clapper coil gets activated. So only the correct clapper (group) coil for Blue#1 is activated but still Yellow#1 and Red#1 get selected while their clapper coil (grounding) is NOT energized? How is that possible?

Any ideas what could cause this?


Additional information:
I'm technical and pretty good with electronics and have the original schematic.
What I've done so far:
-totally cleaned the keyboard, 3-pushbutton group selector and pinbank. Restored the Power Supply Unit and replaced silicium rectifier with new bridge. Cleaned all connectors.
-with the ohm-meter I completely checked the keyboard, group push button bank and pinbank. The only thing that amazes me is that any (of the 120) selection coil gets grounded by ANY clapper coil (group / grounding coil). This must be the reason why I'm having this issue. But I can't find any real error.

So if anyone is willing to help me and has tips etc, all is very welcome! Thanks in advance!

Did you check the contacts of the drum??
Email me i have a schematic of it
tpjm.peters@hotmail.com

I can't add a picture here
So email me

Groet,

Tim

Hi Tim,
Do you mean the clapper contacts on the drum? Yes I did and they all measure with no resistance.
Every selection coil meaasures about 5 ohms iirc; so do the clapper coils.
I think the issue must have something to do with the grounding on the drum / pinbank. When I had the drum on the bench and measured everyting (coils, grounding etc) I noticed that any given selection coils gets grounded by ANY clapper coils, not just 'him own'. I really have my doubts if that's correct but I have no other drum so no reference or comparing. What do you think about this?

Send you a PM with my emailaddress :)
And thanks for your response!

Hello Sabel

As you can see on the diagram, the upper end of the Selection Coils (for example, # 1-blue, # 1 yellow and # 1-red) are connected in parallel. The lower end goes to the 3 different Group Relays. If in fact only one Grolup Coil attracts, but all three Selection Coils are activated, there are two possibilities. Either the contacts on the Group Relays do not open, or there is a short to ground on the Selection coils or in the wiring.

Best regards - charly49

Thanks charly49 for you reply!
Yes what you're saying is what I figured. The 'hot' end of the selection coils powered from the keyboard are indeed interconnected. So yes, # 1-blue, # 1 yellow and # 1-red (which are actually #1, #41 and #81) are directly connected. Yes, only one Group Coil (clapper) is activated (the correct one) so the blue-yellow-red-push button bar is OK. I measured that and checked the coil on selection and it's working correctly: the correct group coil is fired.
So my conclusion is: fault must be in the pinbank/drum.

So what you're saying: 'Either the contacts on the Group Relays do not open, or there is a short to ground on the Selection coils or in the wiring.'
That's the kind of answer I was hoping for :)
I'm almost 100% the group contacts are completely open / free at rest of all six clappers. But ofcourse I'll double check that again.

But what if it's the 2nd possibility? I've already measured every single selection coil, but will do that again. Also measured the wiring (big Jones plug to the drum) and found no errors. Its 20 wires for the selection coils, 6 for the group coils en one ground).
I think the only thing I can do really is do all the measurements again. Altough I'm affraid I not gonna find anything. Maybe give the group contacts a little more clearance? Just to be sure?

One more IMPORTANT NOTE: I don't have this issue with all selections. Most of the selections are fine and just a few make these double or triple selections. So maybe carefully lining up the grouper contacts? (just a thought)

Thanks again!

Stuur me je emailadres

timroy schrieb:
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> Stuur me je emailadres
>
>
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Heb ik al gedaan via PM.
Heb mijn emailadres ook zichtbaar gemaakt via mijn profiel. Dan kun je het daar ook vandaan halen als de PM niet aankomt.

For the others: made my email address public

So I worked on the 1458 selection drum last weekend. Before opening up the drum I ohmed out every single contact and coil on the unit.
I found about 5 selection coils that read lower resistance (about 1.5 to 2.0 ohms) that the rest (around 3.5 ohms). Desoldered one end of the coils and all measured okay. Turned out that the contact strip (ground side of the coils) which makes contact with the clappers had somehow some leakage to the drum housing.
I also gave some extra attention to clapper contacts and especially the contact clearances.
As a result the errors with double or triple selections are gone! That was the weirdest issue and I'm glad it's solved (well, looks like it)

Got 2 more issues with the selection system:
-missing an entire group (yellow 21=40). Group coil does nothing. Coil is OK when I manually provide ground and power to the connector. So gotta trace that some further.
-missing all three #40's. Keyboard contacts on #40 measures 0 ohms. #20 are fine since they use the same wire. So need to trace that one further also.

Okay, just to let you guys know how things are going.
My selection issues are solved. Turned out to be an oldfashioned broken wire in the loom. So all is good now.

Thanks for the support!