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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 5th Oct 2022, 1:05 pm   #21
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

M yeah, it's 6 cm, the pins seem to be matching as well, 50k ohms. It's saying it's 500 mW. I thought this is what the 735 W on mine might be.
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Old 5th Oct 2022, 2:54 pm   #22
theredhouseinn
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Default Re: [HELP] TASCAM Porta 05

Hi Kyle.
Looking at the pic of the track, it looks as though the track is very worn and there appears to be damage at one end. The contact slider looks as though it has a brown deposit on it like coffee has been spilt on it.
From the test result that you have I think that a replacement is the only solution.
John.
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Old 5th Oct 2022, 3:02 pm   #23
DMcMahon
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Default Re: [HELP] TASCAM Porta 05

Quote:
Originally Posted by sourbiscuits View Post
M yeah, it's 6 cm, the pins seem to be matching as well, 50k ohms. It's saying it's 500 mW. I thought this is what the 735 W on mine might be.
500mW is the power rating, i.e. 500 milli Watts / 0.5 Watt / Half a Watt.

Unless the 735 on the old one says 735mW then it has nothing to do with the power rating I would say, a photo showing it might help.

David
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Old 5th Oct 2022, 3:25 pm   #24
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Default Re: [HELP] TASCAM Porta 05

Thank you John! I find it hard to see the damage myself, but the MM test speaks clearly it must be damaged. That's why I am looking into a replacement already.

I am attaching a photo David. I am also thinking to place the black plastic fader holder in case the stock one is not fitting somehow.
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Old 5th Oct 2022, 3:44 pm   #25
DMcMahon
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Default Re: [HELP] TASCAM Porta 05

Maybe the 735W is a type/model number, I do not think it is significant here in terms of a replacement.

David
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Old 5th Oct 2022, 3:48 pm   #26
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

Alright, thanks for the tips David. I'll go for that one. Once I get it, I'll post an update and hopefully solve the thread!

- Kyle
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Old 5th Oct 2022, 11:00 pm   #27
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Default Re: [HELP] TASCAM Porta 05

One thing to check is that the replacement fader you linked to has a linear taper whereas the original fader has an A type logarithmic taper. If you replace a logarithmic fader with a linear fader you will find that the fader has to be set much lower to match the volume of the other channels. You really need to find a fader with an A type taper. They are listed in the data sheet for the fader you linked to but that supplier doesn't seem to sell them.
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Old 6th Oct 2022, 9:18 am   #28
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Default Re: [HELP] TASCAM Porta 05

I would expect those faders to be 10k log*, but you do sometimes see higher values especially on Japanese stuff.

You could relatively easily check whether it's the fader at fault by temporarily replacing it with a potential divider made of individual resistors, say 75%:25% of the nominal fader resistance, as a potential divider (middle goes to the wiper connection, obviously). If everything then behaves correctly, you know for certain that fader is kaput.

Obviously if one end of the fader is supposed to be open circuit, you only need one whole resistor

It doesn't look very well in the pictures, and that design gives three areas for mechanical problems (at least!): The nominally completely-conductive track for the wiper, wiper-to-fader track, and the extreme ends where it connects to the rest of the circuit. You could be chasing your tail forever trying to deal with all of those.

And assuming it is the fader, buy four, at least!

*The correct law is antilog, but that's usually only a thing on professional kit.
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Old 10th Oct 2022, 3:47 pm   #29
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Default Re: [HELP] TASCAM Porta 05

I thank you both for the good information shared! I have not actually ordered anything yet. However, I can confirm the problem was in the fader rather than in the PCB. I ended up using the transport mechanism as a donor for a porta two I recently got. I will be opening another thread for it as I have something going on there. Thank you again all for the help. This thread is solved unless someone has more info to add Hope it helps to other people out there.
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Old 9th Jan 2023, 10:09 pm   #30
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Default Re: [HELP] TASCAM Porta 05

I have an update and facing yet another issue with my porta 05. I received the replacement fader today. I managed to fit it in even though it's slightly different than the original one. I now have volume control over all channels.

So the next thing I want to figure out is why are my channel 1 (the one I fixed) and channel 4 giving me quite a muffled signal compared to 2 and 3. I tried the head azimuth but that does not seem to be the problem. Could this be related to adjustments of any trim pots on the PCB? If not, maybe the play head itself or another PCB component? I am blind guessing here. I am open to any suggestions.
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Old 9th Jan 2023, 10:51 pm   #31
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Default Re: [HELP] TASCAM Porta 05

Probably it is either head wear or dirt on the head. If you look carefully at the head you may see an indentation where the head has worn. Dirt can accumulate at the top and bottom edges of the indentation which won't always be removed by a casual head clean. You need to clean this thoroughly - sometimes I'll use a cocktail stick to remove really stubborn dirt.

Another thing to check is that the head isn't magnetised although a magnetised head is usually noisier than a demagnetised head.

If a thorough clean doesn't fix it then you can get the head re-profiled (aka relapped) for a reasonable cost which will remove the indentation.
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Old 11th Jan 2023, 7:36 pm   #32
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Default Re: [HELP] TASCAM Porta 05

Thank you for the reply James. I did discuss the head state in another thread of mine (for the porta two) where the two units kind of overlapped as I used the porta 05 trasport as a donor for the porta two but took out the heads of the porta two to keep them in the new trasport I installed. So basically, the heads in the porta 05 are what it had initially. I refurbished the transport and it's now working but I am facing the situation in question. I am attaching photos (as detailed as I could make them). I am not entirely sure if I understand the procedure you mention (re-profiled/relapped) and where I might be able to get it done. Either way, I wanted to give you a view of the head and ask if it can even be done given the state I have it in?

- Kyle
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Old 11th Jan 2023, 11:52 pm   #33
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Default Re: [HELP] TASCAM Porta 05

I don't know if it is just a reflection, but it looks like there is some kind of line across the top of the top track of the head and also possibly at the bottom. Can you feel a groove if you run your fingernail across the head? If they use the same head as on the Porta07 then there should not be a groove there.

If you want to get the head relapped then I would suggest contacting Terry Summers at Summertone

https://www.summertone.com/

who is very experienced with this sort of work.
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Old 12th Jan 2023, 12:32 am   #34
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Default Re: [HELP] TASCAM Porta 05

Well said James.

Just taking a good photo of the head face isnt easy. It's microscopic photography. A good photo clearly shows the individual laminations and the critical head gap(s) - which can be sub micron width.

My shot below isnt a good micro photo but it's at least closer to showing the important detail. You can barely see the horizontal laminations.The photo is not detailed enough to show the head gaps. I've circled the area where the vertical gaps would be on tracks 1 and 2.

It's possible to use a mobile phone camera as I did but it usually requires a suitable close up lens clipped onto the phone body over the existing lens.

I've serviced many Portastudios and have often relapped the record/play head. Especially the fast speed Portas (3.75ips) wear the head fairly quickly. The pressure pad in a cassette not only wears cassette heads excessively but unevenly. Sometimes it wears a cavity right over one of the head gaps, seriously compromising the sound on both record and play. I guess there would be a head relap tech in a large city like Amsterdam.
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Old 13th Jan 2023, 6:40 am   #35
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Default Re: [HELP] TASCAM Porta 05

Another thought: photographing the head face with the needed detail can be difficult but it's much easier to just view it using a suitable inexpensive magnifying loupe under a good light. Any wear on the head face should be easy to see.
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