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Old 12th Apr 2017, 12:40 pm   #1
'LIVEWIRE?'
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Question Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

I'm in the process of repairing a Bush SRP30C fitted with the above deck. Someone has fitted one of the Chinese Ceramic Cartridges in the detachable headshell by gluing it in a BSR Turover bracket, fixing the t/o knob & 'flag' in place. So far so good, but (1) they were only using the LH channel of the cart. with the -ve terminal taken to one pin of the 3-pin plug on the headshell, and the +ve terminal to the other pin. No common negative lead was fitted. The cartridge actually worked that way, how I don't know, since one of it's pins was only connected to the 'stereo' socket in the player. I've now fitted a negative lead, commoning the 2 -ve terminals on the cart.
Problem #2 is that I cannot set a tracking weight no matter which way or how much I adjust the screw at the back of the PU arm which is meant to set the stylus pressure. My trusty Garrard Pressure gauge, which I checked for accuracy using the 5g. test weight, will not show a balance at any point on it's scale from <1 to about 12g., though the arm did track several records OK before, out of curiosity, I decided to check the VTF (Stylus Pressure). AFAIK the arm is as Garrard designed, and I can't beleive the VTF is more than 12g, so what can I do to check and set the tracking weight?
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Old 12th Apr 2017, 1:10 pm   #2
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

If it's anything like my Bush SRP41, the 'stereo' socket includes an automatic switch that opens when a plug is inserted. This 'unparallels' the L & R cartridge outputs leaving the R channel to feed the second amplifier.

Listening only to the L channel would certainly miss a certain amount of music!

Regarding tracking weight adjustment, the BSR arm on mine has a rather crudely adjustable counterbalance spring at the hinge end. Is yours missing?

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Old 12th Apr 2017, 2:01 pm   #3
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

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so what can I do to check and set the tracking weight?
It could be that the spring that is adjusted by the screw has weakened over the years. Try shortening the spring a few turns, or, try other springs.
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Old 12th Apr 2017, 2:59 pm   #4
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

It could be the boltnut/nut/spring arrangment has reached the end of its travel or just parted. You could always add a weight to the very end/underside of the tone arm.
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Old 12th Apr 2017, 3:14 pm   #5
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

Surely the little Chinese cart would be lighter than the original (something like a TC8?). Someone hasn't cleverly secreted a lump of lead somewhere in the headshell, have they?
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Old 12th Apr 2017, 6:16 pm   #6
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

Thanks, all, for your helpful suggestions. Today with a bit of fiddling I managed to set the tracking weight to 10 grams, which is the maximum specified by Garrard. The Chinese Cartrige/Garrard Headshell combination weighs about 56g. There's no sign of a lump of lead hidden anywhere in side the pickup assembly. Regarding the stereo connection, on the SRP30C - for some reason Bush used what appears to be a 75 ohm TV aerial socket for this purpose, and there's no switching to bridge the channels, so they'll need to be bridged with a wire. Getting at the spring used to adjust the stylus pressure is impossible without removing the pickup arm, as it cannot be raised enough to see what's inside the rear end.
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Old 12th Apr 2017, 6:37 pm   #7
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

Bridging will allow you to hear all of the content of course, but as you're playng stereo pressings, it would be better all round if you could try to get the tracking down to 5 grams. When fitted with its original Garrard GC2 or GC8 cartridge it would have tracked at c. 10 grams.
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Old 13th Apr 2017, 6:40 pm   #8
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

Looking further at the TA/Mark II today, i realised that the tension spring which controls Stylus Pressure is mounted vertically at the rear of the PU arm. The adjusting screw either stretches or compresses this spring, thereby raising or lowering the stylus , which was almost touching the deck plate. Turnimng the screw anticlockwise raises the head end, and I was able to bring the SP down to 3.5g by this method. I may well leave it at that. My excuse is that I'd never even seen one of these decks before, let alone worked on one!!
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Old 13th Apr 2017, 9:24 pm   #9
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

No excuse needed! You may find that at 3.5g, the arm will track with no problem, but it will be too light to trip the knock-off mechanism. You'll see under the turntable a vertical spring on the lever that is lifted by the turntable centre boss when the pick up reaches the end of the record. Adjusting this screw adjusts the pressure needed to activate the trip.
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Old 13th Apr 2017, 9:55 pm   #10
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

It tripped out OK earlier today, when I played a couple of 7" 33.333rpm record I played, but I will check the trip setting, and adjust it if neccesary. I've downladed the service info for the three speed version of the deck from this site, and I have the user instructions for the exact model, so I should be able to get it running OK!
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Old 14th Apr 2017, 5:42 am   #11
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

Best not to touch the trip mechanism just set tracking weight t 5 grammes. Those cartridges need that.
well done so far.
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Old 14th Apr 2017, 8:25 am   #12
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

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I've downladed the service info for the three speed version of the deck from this site, and I have the user instructions for the exact model, so I should be able to get it running OK!
The earlier Garrard TA 3 speed version differed from the 1956, 4 speed version in some respects. As to whether the knock-off is different, I'm not sure.
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Old 21st Apr 2017, 10:59 am   #13
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

The Deck is running well now, everything works including the turntable brake, Since my last post I've paralleled the two channels of the cartridge so that all the info. on a stereo disc is heard, abbeit in mono. The Bush SRP 30C has a stereo socket (75 ohm TV type for some reason best known to the designer(s)), but without an identical or very similar valve amp. it's never going to be used as a stereo. I'm sure this has been covered before, but, does paralleling the 2 channels of a stereo cartridge increase the output? I would have thought it doubled the voltage, but halved the impedance, but maybe I'm wrong!
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Old 21st Apr 2017, 12:06 pm   #14
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

No it does not double the voltage the element is capacitive rather than resistive.
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Old 22nd Apr 2017, 4:00 am   #15
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

With the channels wired in parallel the voltage is the mean (half the sum), the source impedance is halved, so you should lose fewer millivolts into it.
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Old 22nd Apr 2017, 4:08 pm   #16
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

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With the channels wired in parallel the voltage is the mean (half the sum), the source impedance is halved, so you should lose fewer millivolts into it.
............and the source impedance looks like a series capacitor, so you'll get a more extended LF response into the usual resistive load, as long as both channels are in phase. They usually are in phase at LF in order to keep the stylus in the groove.

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Old 24th Apr 2017, 3:30 pm   #17
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Default Re: Garrard TA/Mark II (4SP) fitted with Chinese Cartridge

AFAIK, the two channels are wired in phase, the volume level is cerainly more than adequate, whilst the sound quality is very good for a record player of this type. What I did was parallel the negative connection in the headshell, then bridge the positive ones under the deck by connecting a short length of wire between the Volume control and the stereo o/p socket. This is easily reversible if or when a suitable similar amplifier is obtained to use as the other channel, but this is highly unlikely. As a matter of interst, if the two channels of the pickup were wired in series, making sure the phasing was correct of course, would that produce a higher o/p. The source impedance would presumably be doubled, so in theory, so would the cartridges o/p voltage, though the higher Z might not be such agood match to that amplifier's i/p. Anyway whenever I've fitted a stereo cartridge in place of a mono one I've wired the two channels in parallel, which usually works well, so I'll leave it at that!
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