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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 15th Apr 2022, 3:01 pm   #1
dragonser
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Default Tandberg Series 15 overhaul

Hi,
I need to get a couple or reel to reel tapes copied and the tape machine I was going to use to copy then has packed up
( not is an easy repairable way ! )
I have a Tandberg series 15 that has been in the round to it pile for too long ! so apart from changing the main belt ( which I have ordered ) is there anything I should get ordered before trying to get it sorted out.
Is the mains filter capacitor a weak point ? I seem to remember reading that here.
Would the main smoothing caps be a good thing to replace ?
Sorry if this has been covered elsewhere...
the tapes are from a Sharp RD 504 and a Sony TC900s
thanks in advance.
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Old 16th Apr 2022, 5:08 am   #2
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Default Re: Tandberg Series 15 overhaul

The two Akilles heels on these Tandbergs are the pinch roller (the rubber tends to go hard with age), and the record-playback switch (depending on the date of manufacture; later models are better). The fix for the former is to get the rubber replaced, and the latter involves judiciously cleaning the contacts.

I haven't had any bad experience with the main smoothing cap, but the capacitor across the motor switch tends to go leaky with age, with the result that the motor runs continuously rather than being stopped in the stop mode. It's actually a resistor-capacitor combo in one package (0.1µF + 47 ohm / 250V AC), but there's no harm in replacing it with separate components.

Another source of trouble in my experience are the felt clutches underneath the reel tables; usually this mainly causes problems during fast wind (slippage) and subsequent stopping (tape spillage). This is more of an adjustment issue than replacing parts though.
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Old 18th Apr 2022, 2:18 pm   #3
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Default Re: Tandberg Series 15 overhaul

Hi, this helps, thank you.
I powered up the machine today, no sound at all ! but after lifting the chassis out of the case I found that someone had disconnected the speaker.
so I reconnected it and found that after a minute or two I get a buzz in the background.
the machine looks I think in good condition.
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Old 18th Apr 2022, 2:39 pm   #4
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Default Re: Tandberg Series 15 overhaul

I have overhauled about a dozen of these.
Things to do:
- New belt (I can supply these if needed, but may take some time)
- Partial stripdown and removal of hard gluey grease and clean of top deck linkages around joystick, brake/wind mech, etc.
- Thorough clean of rec-amp switch (this can be done fairly easily with q tip dipped in contact cleaner.)
- Resurfacing of idler rubber, this gets very noisy in playback especially at 7.5ips. Remove outer few mm to expose fresh surface.
- Replacement of s/c RIFA motor switch suppressor cap +47R resistor.

There can be occasional weird faults such as oscillation if the VU meter bulb is o/c, or if the earthing between internal PCBs is not in tip top shape. Also had one with a failed PTC resistor which gave some really odd symptoms.

The electrolytic capacitors in these rarely give trouble, certainly I've never seen one in need of a 're-cap' which seems to be favoured in many yank forums.

If the machine has lain dormant for years, give it time to 'wake up' by applying mains for a few mins at a time, powering down, and gradually extending the 'on' time. You may find some odd audio faults are simply down to lack of use, the caps may just need some reforming.

You say you have hum. Clean the rec-amp switch first and then try what was mentioned in previous paragraph. Any more probs, ask away!
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Old 18th Apr 2022, 6:26 pm   #5
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Default Re: Tandberg Series 15 overhaul

Hi,
well I managed to get the tape mechanism working. the end of tape sensor switch needed a bit of movement to get it working.
I will investigate further and clean the record playback switch.
I don't think this tape machine has been used for maybe 40 years ?
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Old 27th Apr 2022, 11:10 am   #6
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Default Re: Tandberg Series 15 overhaul

Hi, a quick update.
i have cleaned the record playback and eq switches. This makes it crackle less....
but no sound when playing a tape. I will try the inputs and see if I get any signal on the vu meter in record mode. ( the pp3 in my sine wave generator has gone flat, luckily it hasn't leaked. ). there is no buzz or meter movement when I touch the radio and pu inputs in record mode ...
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Old 27th Apr 2022, 10:21 pm   #7
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Default Re: Tandberg Series 15 overhaul

Is this the 2 track (15-21) or 4 track (15-41) one? If the latter, have you tried the other track positions? I have one where the track selector is a bit 'fussy' or dirty and mutes the audio if not in a certain spot.

You should get a line-level playback from the tape via the 'pre amp' phono socket irrespective of the position of the Rec/Amp switch. Check this.
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Old 28th Apr 2022, 3:48 pm   #8
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Default Re: Tandberg Series 15 overhaul

Hi,
it is a 2 track version. I checked some voltages today and found the voltages around q 208 hardly present.
so I then noticed r222 was burnt. After checking, there was a short circuit on the pre amp side of r222. I unsoldered C214 and yes it has gone short circuit...
I found a replacement 100uf but rated at 63 volt. So have fitted it.
more happens but the sound from the tape playing is very low and distorted.
the voltage on the 10 watt amp midpoint is far too low ( 1 vdc ).
I am going to order some more 100uf caps and check the other ones in the machine.
thank you for all your help.
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