Hi everyone.
I recently obtained a very nice Grundig reel to reel tube tape recorder. It plays okay but I really want to use it for recording.
There are a number of buttons on the front. I know how to set it between mono and stereo, and pick the track sets for mono. Also, I know then when I press a little knob labeled R/S a little indicator tube shows the signal input from my source which is variable via the volume knob on the faceplate.
There are three buttons on the bottom right hand side of the unit. One is labeled like a backwards 'Q', the other a microphone, and the other similar to an omega symbol. It seems that the microphone and omega buttons select different recording inputs but I don't know what the backwards Q one is.
The R/S button also turns clockwise and goes down. If I turn it clockwise with an input, a signal shows on the tube display but with different characteristics.
If I hold the R/S button down and then press play, the unit seems to lock into some sort of record mode, but I get nothing on the tape when I play back.
This problem has really got me stumped. I tested all the tubes and made sure that the power supply and wiring are functional.
The unit looks very similar to the TK line of Grundig players but it came out of a console somwhere in the fiftes or slightly earlier.
Please help me, I can't seem to figure this darn machine out!
I really want to record!!
-- Duo
I recently obtained a very nice Grundig reel to reel tube tape recorder. It plays okay but I really want to use it for recording.
There are a number of buttons on the front. I know how to set it between mono and stereo, and pick the track sets for mono. Also, I know then when I press a little knob labeled R/S a little indicator tube shows the signal input from my source which is variable via the volume knob on the faceplate.
There are three buttons on the bottom right hand side of the unit. One is labeled like a backwards 'Q', the other a microphone, and the other similar to an omega symbol. It seems that the microphone and omega buttons select different recording inputs but I don't know what the backwards Q one is.
The R/S button also turns clockwise and goes down. If I turn it clockwise with an input, a signal shows on the tube display but with different characteristics.
If I hold the R/S button down and then press play, the unit seems to lock into some sort of record mode, but I get nothing on the tape when I play back.
This problem has really got me stumped. I tested all the tubes and made sure that the power supply and wiring are functional.
The unit looks very similar to the TK line of Grundig players but it came out of a console somwhere in the fiftes or slightly earlier.
Please help me, I can't seem to figure this darn machine out!
I really want to record!!
-- Duo
Oh, I just remembered...
The Grundigs of this era used some Wima caps that looked like big Orange Drops (but not orange) which became hydroscopic.
If you disconnect each and measure, you may find they have resistance of a few meg ohms.
Some tape machines had the ability to superimpose onto an existing recording. This was done by switching off the erase head, reducing the bias and signal to the record head.
I wonder if the S/R is superimpose/record - just a guess.
Does the machine play back existing recordings?
Can it erase an existing recording?
Cheers,
The Grundigs of this era used some Wima caps that looked like big Orange Drops (but not orange) which became hydroscopic.
If you disconnect each and measure, you may find they have resistance of a few meg ohms.
Some tape machines had the ability to superimpose onto an existing recording. This was done by switching off the erase head, reducing the bias and signal to the record head.
I wonder if the S/R is superimpose/record - just a guess.
Does the machine play back existing recordings?
Can it erase an existing recording?
Cheers,
A rethink...
The omega is definately mic.
The reversed Q is line-in.
A third symbol (which is like Q rotated 90 deg CCW) is phono pickup.
This input was for a crystal or ceramic cartridge. These cartridges were high output, sometimes line level, and if loaded by 1 meg, would need no EQ.
More useless information where that came from...
Cheers
The omega is definately mic.
The reversed Q is line-in.
A third symbol (which is like Q rotated 90 deg CCW) is phono pickup.
This input was for a crystal or ceramic cartridge. These cartridges were high output, sometimes line level, and if loaded by 1 meg, would need no EQ.
More useless information where that came from...
Cheers
Hmmm very interesting.
The recorder will erase a tape if I try getting it into the so called record mode.
The superimpose option seems logical to me by how it's acting when I go into that mode.
The machine will play existing recordings and it also seems to get the input I feed it. The problem is that the input isn't getting onto the tape. It will erase an existing tape just fine, in fact, quite well, so I'm sure the erase head is working. Just, it seems almost as if the amplifier isn't sending the record signal to the head.
Also, coulf these hydroscopic caps be causing the record problem?
I'll definately check their resistance, maybe even with my megger.
I guess a few megs might throw some bias around a bit, who knows.
The recorder will erase a tape if I try getting it into the so called record mode.
The superimpose option seems logical to me by how it's acting when I go into that mode.
The machine will play existing recordings and it also seems to get the input I feed it. The problem is that the input isn't getting onto the tape. It will erase an existing tape just fine, in fact, quite well, so I'm sure the erase head is working. Just, it seems almost as if the amplifier isn't sending the record signal to the head.
Also, coulf these hydroscopic caps be causing the record problem?
I'll definately check their resistance, maybe even with my megger.
I guess a few megs might throw some bias around a bit, who knows.
If it's not the caps....
The fact that it erases is good news. It means thet the bias oscillator is working. The fault is therefore in the record-amplifier.
Costs were often cut by making some of the circuitry common to record and playback. This meant there was more than a little switching involved. Check the switches that activate when you change from playback to record. They are probably quite dirty, and could be corroded. It is unwise to try to individually clean or retension contacts. Best to try to blow away dust, and if you have some, apply a little switch-cleaner spray, then repeatedly operate the switches.
Good luck
The fact that it erases is good news. It means thet the bias oscillator is working. The fault is therefore in the record-amplifier.
Costs were often cut by making some of the circuitry common to record and playback. This meant there was more than a little switching involved. Check the switches that activate when you change from playback to record. They are probably quite dirty, and could be corroded. It is unwise to try to individually clean or retension contacts. Best to try to blow away dust, and if you have some, apply a little switch-cleaner spray, then repeatedly operate the switches.
Good luck
Is this recorder a TK60 by any chance? The TK60 was the first stereo recorder released by Grundig over here (the UK) in the early '60s.
If it is, or a similar model, it may have two power valves in the bias oscillator stage - Grundig sometimes used an EL95 for generating the erase voltage, and a seperate EL95 for providing the bias voltage. If there is a fault with the latter stage then the recorder will erase alright, but without the bias voltage recording will not be possible, you might get very faint distorted sound at best when you try to record.
If it is, or a similar model, it may have two power valves in the bias oscillator stage - Grundig sometimes used an EL95 for generating the erase voltage, and a seperate EL95 for providing the bias voltage. If there is a fault with the latter stage then the recorder will erase alright, but without the bias voltage recording will not be possible, you might get very faint distorted sound at best when you try to record.
PlusDuo said:
1X EM84 (The indicator).
Grundig TK35 looks closest to me.
Cheers,
http://www.heinffm.de/0199d992c41241201/0199d992da1184701/0199d992da1186204/0199d992da12d831f.html
...The problem is, the TK35 (which electrically the same as the TK30 but with the three speed deck) is a mono recorder, with 1 x EF86, 1 x ECC81, 1 x EL95, 1 x EL84 and 1 x EM84.
Assuming the recorder uses fundamentally the same circuit, but with two channels for stereo, minus EL84 output stages because the recorder used an amp elsewhere in the console, both the EF86s and ECC81s are used on record. the EF86s would take low level inputs such as mikes, the gram setting would go via a high value resistor. The output of the second stage of the ECC81s would feed the stereo recording head. Grundig practice was to have the output from the second half of the ECC81 to go to the head via a resistor/capacitor network, which was shorted out on playback. If the recorder uses just one EL95 for both erase and bias, the bias frequency is much higher than when seperate EL95s are used (78khz as opposed to 40khz).
Assuming the recorder uses fundamentally the same circuit, but with two channels for stereo, minus EL84 output stages because the recorder used an amp elsewhere in the console, both the EF86s and ECC81s are used on record. the EF86s would take low level inputs such as mikes, the gram setting would go via a high value resistor. The output of the second stage of the ECC81s would feed the stereo recording head. Grundig practice was to have the output from the second half of the ECC81 to go to the head via a resistor/capacitor network, which was shorted out on playback. If the recorder uses just one EL95 for both erase and bias, the bias frequency is much higher than when seperate EL95s are used (78khz as opposed to 40khz).
GRUNDIG.
Hi,
In case you need the cicruit diagram, this Dutch gentleman will send it by e-mail for free:
RADIO SCHEMAS
Cheers,
Hi,
In case you need the cicruit diagram, this Dutch gentleman will send it by e-mail for free:
RADIO SCHEMAS
Cheers,
This is definately a stereo recorder. It is four track and has two channels per side of tape. Some of the previousely recorded tapes I have are in stereo. You can either record a mono program on each track, or use a pair of tracks for stereo.
fdegrove: Please do get that schematic, I could really use it.
fdegrove: Please do get that schematic, I could really use it.
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