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Post by rob1948 on Oct 14, 2021 13:04:26 GMT
Hi Norman/Ron,
Progress ! The last issue I had(record is placed on the turn table, tone arm moves across onto the record but immediately retracts and the record is placed back in the magazine) is no longer. I installed the amplifier, connected it up and the problem went away. With the exception of 'sound' the JB is operating nicely from start of record selection to placement back into the magazine. All that is left now is to get the stereo sound working? The guy who supposedly worked on the amplifier said he replaced a faulty transformer and valves. He said he tested it and it had sound, but I am not getting any sound. I have installed a new stylus and set/adjusted the turn table and tone arm according to the service manual, checked the wires and connections from the stylus cartridge to the amplifier, all is good. The problem could be - faulty 'mute relay' in the amp, volume control, stylus cartridge or still some faulty valves (some of them don't 'glow')? I do not have too much faith in the guy who worked on the amplifier.
Would rebuilt JB stereo valve amps be available from the states ? Thanks Rob
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Post by Ron Rich on Oct 14, 2021 13:20:07 GMT
Hi Rob,
If the tubes (OK-"valves" to you ) do not get warm (or glow)-- they ain't working, and you will not get audio ! Try removing the non-working ones and re-seating them. As for the availability--READ our off topic "scams" post--be very careful who you purchase it from !! Ron Rich
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Post by jukenorman on Oct 15, 2021 9:49:07 GMT
Hi Rob,
Is it a Continental 1 (green trims) or Continental 2 (red trims) that you have? I understand from your last post that you have a stereo amplifier. Do you know what transformer was replaced, output of mains transformer? Not that any of the above has any bearing on why you are not getting sound, I'm thinking of possible issues down the line.
I think it's fairly unlikely to be a mute relay issue, it de-energises for sound - although always worth checking the contacts! Anyway, moving the scan switch to off while the record is playing would de-energise the mute relay - easy check to do.
Norman.
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Post by gazzy58 on Oct 16, 2021 10:44:57 GMT
Hi Rob, reading through your text, you have stated that a new stylus has been added, but have you checked the cartridge? What cartridge are you using? If the cartridge is dead you are not going to get any sound. Certainly with old record players if you run your finger over the tip of the stylus when the power is on you will get some noise which tells you the cartridge is working. I have a Continental 1, but if you have the later MK2 version, I believe the sound set up is quite complicated to get it set up properly. If your machine has the correct amp, it will more than likely use the 6973 output valves(tubes). These are getting quite expensive now. If I remember correctly your amp uses 6 of them. I would check that your amp rebuild has included the replacement of the coupling capacitors, or at least make sure they have been checked/tested. I may be wrong, but I have a vague memory of being told that if these fail, you risk damaging the 6973s. There is a conversion that can be done to swap out 6973s for a cheaper equivalent but that requires some rewiring the valve(tube) bases. Other members may be able to advise on this. If your machine is a UK imported machine, it may be fitted with the egg shaped Tannoy cartridge. If so, my advice would be to replace it with a cartridge which is kinder to your records. The Tannoy was nicknamed "The Plough" for a reason. Possibly something like a Stanton would be a good replacement. That's just my opinion. I am sure other members can offer their suggestions on this. Good luck. It looks like you are nearly there. Gary
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Post by rob1948 on Oct 21, 2021 19:45:43 GMT
Hi Ron/Norman/Gary,
Thank you for your replies. I do have some valves that are not glowing or warming up and the 6973 (2 off) are two that are not glowing and others. As Ron says 'If the tubes (OK-"valves" to you ) do not get warm (or glow)-- they ain't working, and you will not get audio!'. The JB is a Continental 2 with a stereo amplifier R2777 and R-2020A Equalizer. I am not sure what transformer was replaced ? I did check the muting relay coil and cleaned the contacts. BUT this is where I am at right now - I have removed the amplifier and sent to a guy in Cape Town who is going to check and rebuild the amp for me. He seams to know what he is doing and has worked on AMI JB amps before. The JB is complete otherwise and selects all 100 records correctly, 'plays' them and places them back in the magazine. Will now just wait for the amplifier and I should be done. As far as the cartridge is concerned I did run my finger over the tip of the stylus when the power was on and there was no noise ? I am not sure where the JB was imported from America or UK but the cartridge is not egg shaped and has the number M44MR on the front. I do have a new 'Shure' M75B with stylus which I think I must fit when I get the amplifier back ? So I will give an update when I get the amplifier back which I don't expect soon but I hope before Christmas. Thanks guys once again for your input and replies. Rob
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Post by Ron Rich on Oct 21, 2021 23:53:44 GMT
Hi Rob,
If the amp is not working, you will not get "noise" by running your finger on the stylus -- the M44's seldom fail ! Ron Rich
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Post by jukenorman on Oct 22, 2021 9:20:54 GMT
Hi Rob, The M44 cartridge will be fine but I would recommend that you fit the more robust stylus ie N44C. Similarly, the M75B is not really robust enough for a jukebox, the N75C is the robust stylus. There is usually an issue mounting "off the shelf" magnetic cartridges in jukebox tonearms like the Continental because they sit too low and it's difficult (impossible?) to get the arm geometry correct. There was a version of the M44C specifically made for jukeboxes where the mounting lugs were cut away at the top such that the cartridge sat partially between the tonearm mounting posts. It may be that you are lucky enough to have one of these M44s? If not, it's quite straightforward to cut away part of the cartridge mounts. I'm pretty sure that I have a stock M44 and a modified M44 in my cartridge collection, I'll add a picture (see below). With regard to connecting the cartridge/amplifier/speakers, it must be done exactly as shown in the manual to achieve stereo-round. Most people fall at the first hurdle by connecting the cartridge channels in phase so that the front facing loudspeakers then produce a subraction of the two channels (usually next to no sound) instead of a summation of the two channels.
Norman. |
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Post by rob1948 on Oct 22, 2021 22:27:19 GMT
Hi Norman/Ron,
Thanks again for this valuable information.Rob
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Post by gazzy58 on Oct 27, 2021 9:42:32 GMT
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Post by rob1948 on Oct 27, 2021 20:11:55 GMT
Hi Gary,
Thank you very much for this information and the link. Yes rather expensive at 78 pounds !!
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Post by Ron Rich on Oct 27, 2021 20:20:29 GMT
Guyz,
In today's economy, I don't find that to be, THAT, expensive ( about $110.00 US) ?? Ron Rich
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Post by rob1948 on Dec 1, 2021 20:21:58 GMT
Hi Ron/Norman,
Still waiting for the rebuild of my valve amplifier. In the mean time is there a colour coded wiring diagram available for the fluorescent lights ? I am considering fitting electronic ballasts to replace the original noisy transformers/ballasts and starters. Only the front panel fluorescent tube is working. Thanks Rob
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Post by jukenorman on Dec 2, 2021 10:31:53 GMT
Hi Rob,
As far as I'm aware there is no colour convention for the wiring of the fluorescent lights. The insulation on the wiring that AMi used for the mains cabling in those days has now deteriorated to such poor quality that it's honestly not worth the effort to retain. A full rewire of the lighting wiring along with the electronic ballasts would be much less hassle, in my opinion! You could also consider LED lighting.
Norman.
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Post by rob1948 on Dec 4, 2021 13:05:49 GMT
Hi Norman,
Thank you Norman you are right and I have actually bought some new but 'old' stock fluorescent fittings with electronic ballasts from our local lighting warehouse with the intension of replacing the current lighting wiring completely and rewiring with these electronic ballasts. I think I must go and buy all their old stock and keep them for future rebuilds. Thanks for your reply. Rob
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Post by rob1948 on Dec 28, 2021 8:08:19 GMT
Good Morning Norman,
When opening the front selector panel there is a red push button micro switch mounted next to the credit light under the top panel. What is this switch for or what does it do ? When I press it a hear a relay activating ? Can you please advise. Further I have rewired the JB lighting circuit and installed LED lights through out as you suggested. Looks good. I decided against the electronic ballasts.(actually I could not work out the wiring for the title panel side lights, gave up and decided to fit LED) Thanks Rob
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