Hi,
A while back i was given a Lem Baby tape echo unit but without the baby..so just the tape unit.
There where written labels on the attached wires so hooking it up shouldn't be a problem..hmmm well
The thing is, that this echo unit is part of a complete unit with a mixer..so i think the tape echo was used like an aux in its original configuration with the mixer...
On the two pcb's attached to the tape unit there is a bridge rectifier + smoothing caps and at the moment im feeding it 12V AC. I replaced the old tape in the cassete with fresh new tape, cleaned and demagnetized the heads and the unit is recording en playing nicely untill the tape completes its cycle..the old recording is still there in full effect...
so no erase...hmmm
Bias is present everywhere on the heads and i get about 1 ohm on the erase head..continuity test on erase head is also okay..
So what i would like to know is what kind of AC is the tape unit expecting? And im guessing that with the correct voltage the bias would work within its specs...
Schematics would be nice..
A while back i was given a Lem Baby tape echo unit but without the baby..so just the tape unit.
There where written labels on the attached wires so hooking it up shouldn't be a problem..hmmm well
The thing is, that this echo unit is part of a complete unit with a mixer..so i think the tape echo was used like an aux in its original configuration with the mixer...
On the two pcb's attached to the tape unit there is a bridge rectifier + smoothing caps and at the moment im feeding it 12V AC. I replaced the old tape in the cassete with fresh new tape, cleaned and demagnetized the heads and the unit is recording en playing nicely untill the tape completes its cycle..the old recording is still there in full effect...
so no erase...hmmm
Bias is present everywhere on the heads and i get about 1 ohm on the erase head..continuity test on erase head is also okay..
So what i would like to know is what kind of AC is the tape unit expecting? And im guessing that with the correct voltage the bias would work within its specs...
Schematics would be nice..
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From memory I think you could expect to see around 20 to 50 volts AC at a frequency of anywhere from 60kHz to perhaps 100kHz. Cheap ferric tapes get away with a lower voltage, chrome and metal need much higher erase fields and consequently higher voltage.
A quite simple solution would be a permanent magnet behind playback heads erasing the tape each. Anyway this is a very crude way to erase magnetic tape giving significant rise to tape noise.
thanks for the replies.
@ mooly
you are absolutly right..i just switched the transformer to one whom gives about 30V AC and yes its erasing now...actually it seems to work flawlessly..
Ive hooked it up as an aux on my Sony MX-P21 which has volume controls on the in and out of the aux...
The only thing i cant get my head around is why the echo isn't repeating...no matter how much i turn the repeat knob there is no repeat effect.
I will check the potentiometer first since the volume pot is crackling to...old machine and corrossion....
But for now im happy with this progress....will post some pics soon.
ps why are all tape echo's mounted horizontally? Has this to to with the motor and its bearings or so?
@ mooly
you are absolutly right..i just switched the transformer to one whom gives about 30V AC and yes its erasing now...actually it seems to work flawlessly..
Ive hooked it up as an aux on my Sony MX-P21 which has volume controls on the in and out of the aux...
The only thing i cant get my head around is why the echo isn't repeating...no matter how much i turn the repeat knob there is no repeat effect.
I will check the potentiometer first since the volume pot is crackling to...old machine and corrossion....
But for now im happy with this progress....will post some pics soon.
ps why are all tape echo's mounted horizontally? Has this to to with the motor and its bearings or so?
Good to hear its working again.
I've got one of those somewhere in one of my studio's gathering large amounts of dust, together with some other Lem tape echo's. I used to collect tape echo's.
Are these worth some bucks?
I've got one of those somewhere in one of my studio's gathering large amounts of dust, together with some other Lem tape echo's. I used to collect tape echo's.
Are these worth some bucks?
That's great news 🙂
(I've never even seen one of these things although I found a few images of it. Looks an interesting project)
(I've never even seen one of these things although I found a few images of it. Looks an interesting project)
LEM Tape Echo pictures
As promised some pics from the LEM tape echo..work in progress, still need to make a back plate etc..the case is made from oakwood 🙂
Actually its similar to the LEM EC10.
As you can see there are three recording heads, one playback head and ofcourse the erase head.
Motor is from Pabst and runs on the AC mains at 220V.
On the front you can engage every rec head separatly or in one go all three...
And about the repeat....im thinking about trying 36V AC maybe the caps arent being charged enough to make the transistor work in the repeat circuit....any thoughts?
Or maybe those tropical fish caps arent charging at all...can some identify the cap on the last pic? ive never seen one like that....
As promised some pics from the LEM tape echo..work in progress, still need to make a back plate etc..the case is made from oakwood 🙂
Actually its similar to the LEM EC10.
As you can see there are three recording heads, one playback head and ofcourse the erase head.
Motor is from Pabst and runs on the AC mains at 220V.
On the front you can engage every rec head separatly or in one go all three...
And about the repeat....im thinking about trying 36V AC maybe the caps arent being charged enough to make the transistor work in the repeat circuit....any thoughts?
Or maybe those tropical fish caps arent charging at all...can some identify the cap on the last pic? ive never seen one like that....
Attachments
This might help with the caps. I'm out of my comfort zone on those older markings and would have to look up how they are derived. We had a similar discussion here part way through the thread though,
http://www.diyaudio.com/forums/solid-state/258614-can-anyone-id-transistor-me.html
Your project looks great, and it all looks clean and in good condition. I'm not sure what to suggest over the repeat issue. Its very much a case of needing to be sat in front of one to get a feel for what is going on. Some of those axial caps could be way past there best by now... might be worth looking into.
http://www.diyaudio.com/forums/solid-state/258614-can-anyone-id-transistor-me.html
Your project looks great, and it all looks clean and in good condition. I'm not sure what to suggest over the repeat issue. Its very much a case of needing to be sat in front of one to get a feel for what is going on. Some of those axial caps could be way past there best by now... might be worth looking into.
So is this just a rip-off of the WEM copycat?, particularly the name 😀
WEM stood for Watkins Electronic Music - what about LEM.
Incidentally, the blue axial capacitors are probably Philips ones?, and as such have been EXTREMELY reliable - but I see a number of tantalum capacitors, and historically they tended to be VERY unreliable (usually going short or leaky).
WEM stood for Watkins Electronic Music - what about LEM.
Incidentally, the blue axial capacitors are probably Philips ones?, and as such have been EXTREMELY reliable - but I see a number of tantalum capacitors, and historically they tended to be VERY unreliable (usually going short or leaky).
whats all this then 😉
Yes, this definitely comes as part of a larger whole; the mixer which accompanies it has a 150 watt amplifier. It was sold under the Univox/Unicord name as the X1 or LEM 10. With two speakers it was sold as the LEM-2.
http://archive-org.com/page/4048968/2014-05-31/http://www.univox.org/pics/catalogs/lempa_catalog.jpg
It appears to not have a speed control. Can't find a schematic for free (one site sells it) but if the motor is DC it's likely you could add speed control or if it's a cap-controlled speed such as IIRC the Klemt Echolette which I'm told could be modded with a switch to at least add other rates.
Best wishes for getting it back into tip-top working condition!
Yes, this definitely comes as part of a larger whole; the mixer which accompanies it has a 150 watt amplifier. It was sold under the Univox/Unicord name as the X1 or LEM 10. With two speakers it was sold as the LEM-2.
http://archive-org.com/page/4048968/2014-05-31/http://www.univox.org/pics/catalogs/lempa_catalog.jpg
It appears to not have a speed control. Can't find a schematic for free (one site sells it) but if the motor is DC it's likely you could add speed control or if it's a cap-controlled speed such as IIRC the Klemt Echolette which I'm told could be modded with a switch to at least add other rates.
Best wishes for getting it back into tip-top working condition!
those are not tantalums but strangly formed tropical fish caps, but i think one of the Philips caps is bad...even by touch a hum is audible...will change that one..
But ive changed the AC input from 30V to 36V and im getting faintly hearable repeats...but its more like a decaying sound.
When engaging rec head three (farmost of the playback head) with repeat down the echo is immediatly cut off, with repeat full open i can hear a faint repeat....so closed and open are sounding different which is good.
My hunch is that maybe one of the transistors is dead which should amplify the repeat signal....this will need further investigation....but im almost there 🙂
Now to identify the tranny...there are no markings on them as far as i can see....but first let take some measurements....
Regarding the motor...
Unfortunatly this is an AC motor and not a DC one...i own a Klemt Echolette S NG51 which indeed has two speeds but those motors have different windings to control the speed of the motor by adding or extracting a winding...so it wont be possible to add speed control in the way of the Klemt.
Thnx for pointing out that thread!
According to this link http://frank.pocnet.net/other/Philips/ColourCodeRC1966.pdf
the ones looking like tantalums are actrually "pin up caps" sexy!
btw the big silver cap in my LEM is made by Ducati 😀
Some usefull information on pin-up caps
Capacitor - Wikitronics
scroll to halfway the page...it also explains the code 😉
Capacitor - Wikitronics
scroll to halfway the page...it also explains the code 😉
Hi g33ks, sorry for reviving and old thread but I have an LEM Baby Tape Echo and I think the erase head doesn't work. Can anyone point me to where I should connect the 30V~ to the head?
I also want to control the motor speed - is it a capstan 3-phase motor? (or what it is called)
I also want to control the motor speed - is it a capstan 3-phase motor? (or what it is called)