Martic solid state AC/DC phonograph - UK Vintage Radio Repair and Restoration Discussion Forum

andysworkshop · 30th Mar 2020, 5:06 pm

Martic solid state AC/DC phonograph - Has anyone know of this make??

Cheers

TonyDuell · 30th Mar 2020, 5:11 pm

I assume the 'DC' means it will run on batteries, not that it can run on DC mains.

I have something similar of a different make that I have forgotten. (I'll try to dig it out sometime soon). Runs off a 6v battery (4 cells, I forget if they're C or D size) or mains. Mine is also an AM (Medium Wave) radio. Inside there's one PCB with the componets you'd expect for a cheap radio with a switch to turn on the turntable motor and connect the audio amplifier either to the radio detector stage or the pickup cartridge. But I've never managed to find information on mine either

andysworkshop · 30th Mar 2020, 5:34 pm

Sounds good, does yours work plus would it be up for sale?? only if it works

TonyDuell · 30th Mar 2020, 6:00 pm

Sorry I am not selling it, one of my minor collecting interests is 'portable audio'. And I've not got it working yet (I know the battery holder in mine is cracked, for example).

Do you have a non-working one? I might be tempted to trace out the circuit of mine if there is any real interest, but it would take some time to do it.

hamid_1 · 31st Mar 2020, 1:11 am

I do remember the brand name MARTIC as I once had an 8 track cartridge tape player bearing that name. It wasn't portable, but it was a very compact mains-powered unit with separate speakers, designed to fit on a bookshelf. I think it was made in Japan, though I'm not 100% sure now - I sold it online many years ago to someone in Scotland. I also don't know exactly who made Martic products. I'm assuming Martic was not an actual manufacturer, just a name used by an importer or distributor. Back in the 1970s when this unit was made, it was common to find cheap radios and other electronic items with a multitude of different names, yet they were all very similar and probably came from the same factories in the Far East.

Sometimes the instruction leaflets with these items included a schematic diagram, often in very small print. If you're very lucky, there might be a copy pasted inside the back of the unit. If not, these things were normally quite basic designs using discrete components; fault-finding is usually not too difficult.

Don't expect high quality audio from this type of record player. They were mainly for fun, for children's bedrooms or taking on holiday. If you're serious about vinyl records, buy something else of better quality. Having said that, I do have a few portable record players and have had some fun from them. For me, collecting and repairing them is part of the fun.

TonyDuell · 31st Mar 2020, 10:56 am

I've dug mine out. It's a 'Tempest 711AC' but otherwise looks very similar to the one above. There are stylng differences (the biggest being that the handle is the front when you use it as a record player) but a similar turntable/pickup, 4 knobs (speed, radio/record player select, tuning, on/off-volume) in a line, etc.

Mine uses 6 transistors and 3 diodes on a single PCB inside. I did take a few minutes to trace out the circuit diagram which I've attached if anyone is interested.

Chris55000 · 2nd Apr 2020, 9:45 pm

Hi!

I've had a look at the circuit diagram and the bias components that should be between the bases of the Output transistors Q5 & Q6 are missing – there's a 33uF "bootstrap" capacitor you've drawn between the junction of the 330 ohm and 470 ohm resistors to the centre–point of the o/p transistors, Q5 & Q6 emitters is correct as you've drawn it, but there should also be a lower resistance component (it may actually be an N.T.C. thermistor, typically 33–68 ohm cold) between Q5 and Q6 bases to complete the load circuit for Q4.

I have mentioned this component as it's important for setting the quiescent (no–signal) current of the o/p transistors, which are almost certainly germanium, and would overheat very rapidly if it went o/c or a lead broke off it or the PCB here!

Interesting is the use of the 2nd i.f. stage as an emitter–follower to provide the relatively high–impedance needed for the crystal cartridge used on the player deck – it's not a reflexed amplifier as this functions as a conventional tuned i.f. amplifier on radio!

I'll be happy to redraw your diagram neatly when I have a bit of time spare!

Chris Williams

PS!

I can identify the bias components for you if you post a good clear picture of the PCB near the output transistors!

TonyDuell · 3rd Apr 2020, 6:23 am

I thought there should be a DC path too but I couldn't find it. I don't think I could get any sensible DC resistance between Q5 and Q6 bases either. I'll take another look in the next few days. The obvious thing would be if that thing I labelled as a 22pF capacitor (which seems a very low value for something in an audio output stage) is in fact a thermistor. It tested open-circuit on my meter though. It looked like a small (bead-like) capacitor but with no markings and a dot on one end.

Could it perhaps be a number of diodes in series? Too many for the diode test range on my meter to identify it as such.

Chris55000 · 3rd Apr 2020, 8:18 am

Ah!

Almost certainly a miniature double–diode unit – the dot will most likely denote the cathode end, which will be connected to the base of Q6 and the collector of Q4!

Chris Williams

60 oldjohn · 3rd Apr 2020, 9:35 am

Quote:

Originally Posted by TonyDuell

I assume the 'DC' means it will run on batteries, not that it can run on DC mains.

I have something similar of a different make that I have forgotten. (I'll try to dig it out sometime soon). Runs off a 6v battery (4 cells, I forget if they're C or D size) or mains. Mine is also an AM (Medium Wave) radio.

Philips 423 and 270 are similar style portable players, but no radio.

John.

TonyDuell · 3rd Apr 2020, 10:38 am

Quote:

Originally Posted by Chris55000

Ah!

Almost certainly a miniature double–diode unit – the dot will most likely denote the cathode end, which will be connected to the base of Q6 and the collector of Q4!

Chris Williams

Yes, you're right. I've tested it again and it does show a 1.3-ish voltage drop (out of circuit). And the dotted end does indeed go to the collector of Q4.

I've attached the updated circuit diagram.

andysworkshop · 3rd Apr 2020, 3:43 pm

I noticed on the dials that the numbers and letters have faded or come off, is there a way to replace them or does anyone have any spare dials for this model?

Cheers

30th Mar 2020, 5:06 pm	#1
andysworkshop Tetrode Join Date: Aug 2013 Location: Fakenham, North Norfolk Posts: 91	Martic solid state AC/DC phonograph Martic solid state AC/DC phonograph - Has anyone know of this make?? Cheers Attached Thumbnails

30th Mar 2020, 5:11 pm	#2
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Martic solid state AC/DC phonograph I assume the 'DC' means it will run on batteries, not that it can run on DC mains. I have something similar of a different make that I have forgotten. (I'll try to dig it out sometime soon). Runs off a 6v battery (4 cells, I forget if they're C or D size) or mains. Mine is also an AM (Medium Wave) radio. Inside there's one PCB with the componets you'd expect for a cheap radio with a switch to turn on the turntable motor and connect the audio amplifier either to the radio detector stage or the pickup cartridge. But I've never managed to find information on mine either

30th Mar 2020, 5:34 pm	#3
andysworkshop Tetrode Join Date: Aug 2013 Location: Fakenham, North Norfolk Posts: 91	Re: Martic solid state AC/DC phonograph Sounds good, does yours work plus would it be up for sale?? only if it works

30th Mar 2020, 6:00 pm	#4
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Martic solid state AC/DC phonograph Sorry I am not selling it, one of my minor collecting interests is 'portable audio'. And I've not got it working yet (I know the battery holder in mine is cracked, for example). Do you have a non-working one? I might be tempted to trace out the circuit of mine if there is any real interest, but it would take some time to do it.

31st Mar 2020, 1:11 am	#5
hamid_1 Heptode Join Date: Aug 2009 Location: High Wycombe, Bucks. UK. Posts: 811	Re: Martic solid state AC/DC phonograph I do remember the brand name MARTIC as I once had an 8 track cartridge tape player bearing that name. It wasn't portable, but it was a very compact mains-powered unit with separate speakers, designed to fit on a bookshelf. I think it was made in Japan, though I'm not 100% sure now - I sold it online many years ago to someone in Scotland. I also don't know exactly who made Martic products. I'm assuming Martic was not an actual manufacturer, just a name used by an importer or distributor. Back in the 1970s when this unit was made, it was common to find cheap radios and other electronic items with a multitude of different names, yet they were all very similar and probably came from the same factories in the Far East. Sometimes the instruction leaflets with these items included a schematic diagram, often in very small print. If you're very lucky, there might be a copy pasted inside the back of the unit. If not, these things were normally quite basic designs using discrete components; fault-finding is usually not too difficult. Don't expect high quality audio from this type of record player. They were mainly for fun, for children's bedrooms or taking on holiday. If you're serious about vinyl records, buy something else of better quality. Having said that, I do have a few portable record players and have had some fun from them. For me, collecting and repairing them is part of the fun.

2nd Apr 2020, 9:45 pm	#7
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,870	Re: Martic solid state AC/DC phonograph Hi! I've had a look at the circuit diagram and the bias components that should be between the bases of the Output transistors Q5 & Q6 are missing – there's a 33uF "bootstrap" capacitor you've drawn between the junction of the 330 ohm and 470 ohm resistors to the centre–point of the o/p transistors, Q5 & Q6 emitters is correct as you've drawn it, but there should also be a lower resistance component (it may actually be an N.T.C. thermistor, typically 33–68 ohm cold) between Q5 and Q6 bases to complete the load circuit for Q4. I have mentioned this component as it's important for setting the quiescent (no–signal) current of the o/p transistors, which are almost certainly germanium, and would overheat very rapidly if it went o/c or a lead broke off it or the PCB here! Interesting is the use of the 2nd i.f. stage as an emitter–follower to provide the relatively high–impedance needed for the crystal cartridge used on the player deck – it's not a reflexed amplifier as this functions as a conventional tuned i.f. amplifier on radio! I'll be happy to redraw your diagram neatly when I have a bit of time spare! Chris Williams PS! I can identify the bias components for you if you post a good clear picture of the PCB near the output transistors! __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! Last edited by Chris55000; 2nd Apr 2020 at 9:53 pm.

3rd Apr 2020, 6:23 am	#8
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Martic solid state AC/DC phonograph I thought there should be a DC path too but I couldn't find it. I don't think I could get any sensible DC resistance between Q5 and Q6 bases either. I'll take another look in the next few days. The obvious thing would be if that thing I labelled as a 22pF capacitor (which seems a very low value for something in an audio output stage) is in fact a thermistor. It tested open-circuit on my meter though. It looked like a small (bead-like) capacitor but with no markings and a dot on one end. Could it perhaps be a number of diodes in series? Too many for the diode test range on my meter to identify it as such.

3rd Apr 2020, 8:18 am	#9
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,870	Re: Martic solid state AC/DC phonograph Ah! Almost certainly a miniature double–diode unit – the dot will most likely denote the cathode end, which will be connected to the base of Q6 and the collector of Q4! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

3rd Apr 2020, 3:43 pm	#12
andysworkshop Tetrode Join Date: Aug 2013 Location: Fakenham, North Norfolk Posts: 91	Re: Martic solid state AC/DC phonograph I noticed on the dials that the numbers and letters have faded or come off, is there a way to replace them or does anyone have any spare dials for this model? Cheers