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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 21st Sep 2020, 1:04 pm   #1
lukeakascooter
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Default Grundig TK17L restoration help

Hi, I know electronics pretty well to know what components are what, but the details of them not so much and with a project like this it would be shame to see it be completely bricked!

If anyone can help me identify and provide links me to the stuff I need to replace everything that would be so kind of you. My parents want to capture what they think to be an old recording of them and this is the player we ended getting as it was cheap.

I have schematics which were somehow preserved for this entire time lol but again I haven't got a clue how to read them properly other than oh that's a resistor. Etc. I have also taken pictures of the main board and I can tell for sure some things are blown but to be honest replacing all of them seems to be good practice anyway. The underside of the board as well looks super bodge if anyone can see a problem with it. The rest of the unit is actually in pretty good condition so I am not worried about it just yet, just want it to turn on safely before anything else. oh yeah I am aware of the 800ma fuse missing, already ordered a replacement

Photos are attached to this post and I'll make another post with 3 more.
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Old 21st Sep 2020, 1:09 pm   #2
lukeakascooter
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Default Re: Grundig TK17L restoration help

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Old 21st Sep 2020, 1:35 pm   #3
DMcMahon
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Default Re: Grundig TK17L restoration help

Do you know if the 800mA fuse is missing because it had blown ? Was there any previous history of problems ?

These boards can look pretty tatty/stressed, yours maybe looks a bit more stressed than normal. Same with some of the old resistors. The large amount of flux around the soldered connections at the components is typical on these boards.

Looking at the photos quickly I would not condemn anything out of hand.

Do you have a multimeter for measuring resistance and voltage, also what about a scope ?

For any live testing, your personal safety should be paramount. Remember that capacitors (particularly ones like the dual metal can one in your photo # 5) can hold a charge for some time. So for any internal (non powered) investigations leave at least 15 minutes after powering down, before going inside and make sure the mains connector is pulled out from the room socket.

David

Last edited by DMcMahon; 21st Sep 2020 at 1:46 pm.
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Old 21st Sep 2020, 1:45 pm   #4
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Default Re: Grundig TK17L restoration help

Yeah I had taken out the fuse as it was the first thing I discovered that I knew was 100% blown so I've ordered one (still awaiting in the post). which leads me to believe there is something else wrong that would of made it blow?

No idea on any history of this unit, there was a tape head alignment done in 1968 but nothing else was with the documents it came with.

I have a multimeter but I am not too experienced on how to use it sadly. no scope.

the unit never turned on and its been unplugged for at least a day now.
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Old 21st Sep 2020, 1:57 pm   #5
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Default Re: Grundig TK17L restoration help

The fuse was blown and I removed it as I already have a replacement one on its way. it is 2nd hand so I have no idea of any history sadly.

thanks for clearing that up, even the really fat burned looking resistors, i took close up shots of them? they look blown to me?

I do have a multi meter but I am not too experienced with it.
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Old 21st Sep 2020, 4:43 pm   #6
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Default Re: Grundig TK17L restoration help

OK all clear.

Do you have 1 fuse on its way or several ? Do you have a soldering iron, OK with basic soldering ?

Often there will be a fault situation for a fuse to blow (fault can be intermittent though) but occasionally a fuse can fail due to age, you may be lucky in that it is an age related failure.

Different people will have different approach ideas, so others may advise differently/better than my suggestions.

First check the fuse value inside your 3 pin mains plug, often it will be 13 Amps which is far too high, I would recommend no higher than 5 Amps, ideally 2 Amps, I use 1 Amp.
(2 and 1 amp are not so easy to find nowadays).

Note - with a 1 Amp fuse, probably also a 2 Amp, in a fault condition the plug fuse may blow before the 800mA internal fuse, this is because the plug fuse is fast acting compared to the internal fuse which is slow acting/surge resistant.

Assuming your mains cable to the recorder is 3 core, use your multimeter set to resistance and connect the meter leads from the 3 pin plug earth pin (top long pin) to the internal metalwork of the recorder. You should get good continuity/very low resistance, this proves you have a good earth connection which is important for safety.

If you connect/short the meters leads together you should also see the same sort of very low reading.

Before powering up, fit the replacement fuse and switch it on at the recorder "On" switch (not connected to the mains). Using your meter (once again set to Resistance) with one lead touching the plug earth pin, then touch the other meter lead to the Live pin and then to the Neutral pin, there should be a very high resistance each time (a short or a low resistance is bad).

This just proves there is no serious short or low resistance at the mains wiring connections into the recorder, it is only a low voltage check so is not full proof.

Connect the meter (recorder still switched on but not connected the mains) across the Live and Neutral pins, you should get a lowish resistance less than 100 ohms but probably higher than around 40 ohms. This checks the mains transformer primary winding is good.

If all Ok then would suggest you measure the resistance from the internal 125mA DC fuse (HT supply) to earth, once again should not be low resistance. If OK then measure the resistance again to earth across both ends of the resistor shown in your photo #5 i.e. connected across the dual large metal can capacitor. The resistor is 4K7 (4,700 Ohms) colour band code Yellow, Violet, Red (silver band at end is a % tolerance).

It is good practice before doing any resistance measurements on capacitors to first measure the capacitor to make sure it is discharged by measuring across the capacitor for DC voltage. In the case of the resistor above measured at each end of the resistor to earth/metalwork.

Note - when doing the internal resistance measurements from the fuse and the resistor you will see some resistance readings due to capacitors charging and other internal circuitry but not a short circuit or very low continuous reading.

More in next Post.

Last edited by DMcMahon; 21st Sep 2020 at 4:49 pm.
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Old 21st Sep 2020, 5:07 pm   #7
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Default Re: Grundig TK17L restoration help

Quote:
Originally Posted by lukeakascooter View Post

thanks for clearing that up, even the really fat burned looking resistors, i took close up shots of them? they look blown to me?
I assume you mean the 22k (22,000 Ohms) Red, Red, Orange resistor in Photo 2. It does possibly look a little swollen/heat stressed but may be fine.

I do not think the others look overly suspicious.

Certainly using your meter again, measure across any suspect resistor to see what resistance reading you get.

Possible trouble with in circuit measurements is that depending upon other connections to the component with series/parallel connected components you can sometimes get misleading resistance measurement, in those situations you then have to disconnect one end of resistor and measure it again.
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Old 21st Sep 2020, 5:43 pm   #8
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Default Re: Grundig TK17L restoration help

If nothing untoward is found with resistance measurements then I would say you then would be ready to try powering up the recorder.

But first read this link - https://www.vintage-radio.net/forum/...ad.php?t=73399

Not easy to explain this, but it is to do with old paper capacitors (particularly the waxy type) that degrade and electrically leak. This potentially can be problematic, especially when the capacitor is coupling the output (anode) of one valve to the input (grid/control grid) of the next valve. In the case of an output valve driving a loudspeaker via an output transformer (like the TK 17) worst case it could be very serious. You will see a lot of information on this subject in the various Forum Threads.

Capacitors normally block DC voltage, when they become leaky they can pass DC voltage which is potentially the problem scenario.

For the TK 17 there are 2 capacitors that together serially couple the anode to the grid of the output valve, C10 and C13, so both would have to be leaky to cause a problem. I think the type of capacitors in the TK 17 are low risk. There are tests that can be done to establish better if the capacitors are leaky.

For instance, before powering up, remove the output valve, the ECL 86, then power up.

There should be minimal (if any) DC voltage at the control grid (pin 8) of the ECL 86, the 10k resistor R29 connects to pin 8. Any appreciable DC voltage at pin 8 indicates that C10 and C13 are leaky.
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Old 21st Sep 2020, 5:52 pm   #9
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Default Re: Grundig TK17L restoration help

Quote:
Originally Posted by DMcMahon View Post
If all Ok then would suggest you measure the resistance from the internal 125mA DC fuse

Update - some versions will have a 150mA fuse.
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Old 21st Sep 2020, 6:05 pm   #10
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Default Re: Grundig TK17L restoration help

Quote:
Originally Posted by DMcMahon View Post
Quote:
Originally Posted by lukeakascooter View Post

thanks for clearing that up, even the really fat burned looking resistors, i took close up shots of them? they look blown to me?
I assume you mean the 22k (22,000 Ohms) Red, Red, Orange resistor in Photo 2. It does possibly look a little swollen/heat stressed but may be fine.
Correction - Photo 2 should have read Photo 3. Also BTW it is R11.
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Old 21st Sep 2020, 6:15 pm   #11
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Default Re: Grundig TK17L restoration help

Photo 2 resistor is R36 4K7 (4,700 Ohms) colour band code Yellow, Violet, Red.

This type of carbon resistor often looks like this.

Last edited by DMcMahon; 21st Sep 2020 at 6:19 pm. Reason: Update
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Old 21st Sep 2020, 7:14 pm   #12
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Default Re: Grundig TK17L restoration help

Thank you for your reply, some of it sounds pretty new to me, but understand and I can do the first few tests you stated as for soldering I like making simple led circuits and modding video game consoles so I have some ok skill so should be ok if I need to replace anything.

I have x5 800ma fuses on the way, so if any blow I have 5 tries to get it right or else I am ordering more lol.

The person I bought the player off did say someone who wanted to buy changed the original old UK style round pin plug to a modern UK plug which is a 13amp fuse, might explain the blown internal 800ma fuse?

I will try the more complicated stuff after the simple tests with the new 800ma fuse. thanks again for all this info I would be all in the dark, I will post all of my progress here for you to see and would appreciate any more help going forward
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Old 21st Sep 2020, 10:41 pm   #13
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Default Re: Grundig TK17L restoration help

The 800mA internal fuse should not blow regardless of the value of the fuse in the plug, it is just better both for the recorder and for personal safety to have a lower fuse than 13 Amps.

Do you know what type of fuse you are getting fast or slow blow ? it should be a slow blow type, typically the fuse value would be preceded by a letter denoting the fuse acting speed, e.g. for normal slow blow the letter is T (Trage), so the fuse would read "T800mA" or "T0.8A"

If the 800mA replacement fuse blows, then that would indicate that there is a fault, lets hope it does not blow, fingers and toes crossed.

David
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Old 23rd Sep 2020, 10:13 am   #14
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Default Re: Grundig TK17L restoration help

Yes its a T800ma came in the mail today, will start doing the tests now
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Old 23rd Sep 2020, 11:49 am   #15
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Default Re: Grundig TK17L restoration help

AND IT WORKS!!! thanks a lot the first part of your advice it was perfect, I did have to test it with the 13amp fuse quickly to see if it turned on but I have found a 3 amp fuse that works too. So the internal 800ma fuse must of blown a long time ago hence why the others couldn't get it working.

first thing that played was a recording of my dads dad (my grandad) never heard his voice either as he passed before my birth, quite emotional for my parents to listen to as well.

ill try upload a video at some point of it working here, again thank you so much for your help and time David. (DMcMahon)
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Old 23rd Sep 2020, 12:47 pm   #16
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Default Re: Grundig TK17L restoration help

That is great feedback, am glad it came good.

David
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Old 11th Oct 2020, 11:29 am   #17
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Default Re: Grundig TK17L restoration help

Here is the link to the video I finally made of the unit working, again thanks to everyone who helped, my dad got to listen to his parents and his young self for the first time in over 30 years or so.

https://www.youtube.com/watch?v=iIP4lLIciag

https://www.youtube.com/watch?v=iIP4lLIciag

I must say that although the unit works, like stated in the video... it seems a little weaker than it should especially the recording and rewinding, some other videos online suggest replacing caps.etc and should restore it back to normality.
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Old 11th Oct 2020, 12:28 pm   #18
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Default Re: Grundig TK17L restoration help

Interesting to see the video clip.

This particular vintage/series of Grundigs do not suffer much with capacitor problems, impossible to be sure without testing/replacing capacitors.

If you have not done it already make sure the faces of the heads are really clean, using a cotton bud to gently clean them using IPA (Isopropyl alcohol/Isopropanol not beer), methylated spirits or just spittle if nothing else suitable available.

Rewind can be somewhat weak on this series, particularly when the left hand Supply spool is heavily loaded with tape. Check that the drive belt that goes from the motor pulley to the flywheel is not slack/slipping, unlikely as if it was you may also get Play/Fast Forward issues.

Make sure that the Supply Reel Table can be easily rotated by hand (brake off), if not strip table, clean and lubricate the mounting shaft, if it was stiff may also affect Play performance.

Make sure that the Supply spool table black plastic outer edge is clean/not greasy, also the top of the metal pulley that drives the Supply table in Rewind. A flat drive belt or even a rubber band (not too fat otherwise may foul the Supply table brake in Play/Fast forward) tightly put around the circumference of the Supply reel table may help to improve the friction contact to the motor pulley in Rewind.

David
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