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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 30th Sep 2022, 7:30 pm   #1
sourbiscuits
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Default [HELP] TASCAM Porta 05

Hello again.

I am here with another riddle.

I recently got a TASCAM Porta 05. The unit seems to have something tangled in the electronics. The best way to describe it is with a cassette that has side A and B.

Basically, when I hit play, channel 3 is somehow routed to the master output and with all faders down, if I move the master up, track 3 is playing all the time (backwards since this is the left track of the other side of the tape). The fader is reacting if I move it up and the signal gets stronger but when all the way down, the channel is playing with a rather decent level.

So basically, channel 3 is constantly playing. What might cause this I am really baffled? Could it be a component gone wrong or maybe I should go for a contact clener throughout the faders?

Please, give me any suggestions. I will share a short video soon to demonstrate if this doesn't help describe the issue.

I am yet to play with recording. I will post again in the mean time.
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Old 30th Sep 2022, 11:46 pm   #2
jamesperrett
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Default Re: [HELP] TASCAM Porta 05

The channel 3 fader has probably lost its ground connection.
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Old 1st Oct 2022, 10:22 am   #3
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

Would that not result in no signal from that channel at all?
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Old 1st Oct 2022, 11:59 am   #4
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Default Re: [HELP] TASCAM Porta 05

Ok, so I cleaned the faders with contact spray. There is a fair amount of dirt built up in and around them. Unfortunately, no change whatsoever. I also noticed today, that channel 1 fader is losing the signal completely when I apply a bit of movement to it. I would have to touch it again to get it going again. I don't see bad soldering points on the bottom. Could that indicate just faders went bad?
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Old 1st Oct 2022, 12:10 pm   #5
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Default Re: [HELP] TASCAM Porta 05

Hi there.
I have had trouble with these faders before. The resistive track is fixed at each end by a rivet. The track can crack at the rivet and become intermittent. I have drilled the rivets out and fixed the track with a small screw, washer and nut. The washer makes the connection good. The downside is that the slider knob will only go up to the 9 position but better than nothing.
John.
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Old 1st Oct 2022, 12:17 pm   #6
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Default Re: [HELP] TASCAM Porta 05

Thank you for the response John!

Right, so it is the fader itself that I should look into. I keep going back to the same conclusion... Could I also go for replacing the entire fader? I have been struggling to find the service manual for the unit as well. I don't have a clue what fader values I should look for if I go for a new fader. Any input on that?

- Kyle
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Old 1st Oct 2022, 12:32 pm   #7
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Default Re: [HELP] TASCAM Porta 05

Hi Kyle.
I have not seen the 05. My time as service manager at Tascam was when the 144 was current, the rest came after I left the company.
Service manuals are obtainable on the web, just type in "porta 05 service manual" and you will find one.
The value of the slider will be marked on the slider body.
there are plenty of sliders available on the net, but the trouble is finding one the correct size.
You won't know if the slider is the problem until you take it out and test it.
John.
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Old 1st Oct 2022, 1:55 pm   #8
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

Yeah, I actually went to disorder the slider off the pcb after my last post. I will measure it with a multi meter and see what that says. After that I will take it apart to further inspect if there's a visible problem. I'll post again after I do that.

As for the replacement fader I did see the values on the side as you suggested. I also thought the size will be the tricky part of finding a replacement. I will also look into that tonight.

Thanks for the inputs again!

- Kyle
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Old 1st Oct 2022, 5:23 pm   #9
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Default Re: [HELP] TASCAM Porta 05

Success! I opened the fader, cleaned it throughout. After I soldered it back in, it worked like a charm. There was quite a bit of dirt in there. I did the same with channel one. It no longer has an issues with the signal dissappearing. I just wonder if which are the trim pots for adjusting the output levels? Should I drop a photo of the pcb?
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Old 1st Oct 2022, 10:40 pm   #10
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Default Re: [HELP] TASCAM Porta 05

All my hype was for nothing.. After I went to put the unit back together, the problem occurred again. I tried redoing the soldering but that didn't help. It would come and go very randomly.. At the end of the evening I just assembled the unit giving up on it for the day. The fader was working and no signal was coming when all the way down. I later turned it on again and it was back at it again. I have really no clue what this is...
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Old 2nd Oct 2022, 9:41 am   #11
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Default Re: [HELP] TASCAM Porta 05

After a thorough investigation of the pcb's I found these two resistors that appear to be in bad shape. Now one obviously looks faulty - not sure if it's corroded or blown. The issue is I can't tell what the last stripe color is. Based on the other resistors that start with the same pattern it should be gold but I am unsure. Since I can't find the schematic online how could I confirm the residence? The second resistor has a spot on it. Is that paint or is it faulty?
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Old 2nd Oct 2022, 10:42 am   #12
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

Replaced both resistors. No change whatsoever...
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Old 2nd Oct 2022, 10:46 am   #13
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Default Re: [HELP] TASCAM Porta 05

Yes R503 does not look healthy, from its brown, black & orange bands it should be 10kOhms, if the 4th band is gold then that is +/-5% tolerance, should be easy to measure may have to lift one end.

Unsure if the spot on R402 is anything to worry about (probably not), its first 3 bands of brown, black, brown indicate that it should be 100Ohms.

David
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Old 2nd Oct 2022, 11:02 am   #14
Nickthedentist
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Default Re: [HELP] TASCAM Porta 05

I suspect something has been spilled into it in this area, at some point in the distant past.

This may or may not have anything to do with the fault which you have.
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Old 2nd Oct 2022, 11:20 am   #15
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

I did the same thinking guys. I replaced both R, however, the ones I have are +/- 1% tolerance. I'm not sure if that makes an impact? I am getting the same behavior. I even tried the device without R402. Same thing happens. It's very weird how it would sometimes work for a bit. Today, I haven't managed to get it to work unlike yesterday.

As for the spillage, I suspect the same. I do not see any marks anywhere on both pcb's though.
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Old 2nd Oct 2022, 11:29 am   #16
DMcMahon
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Default Re: [HELP] TASCAM Porta 05

I do not know the function of these resistors in the circuit but using the tighter tolerance (1%) is fine.

David
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Old 2nd Oct 2022, 11:34 am   #17
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

That should rule out the resistors. I tried after replacing each one. I will continue looking but share any suggestions where to focus. What potential issues could a spillage do and where?
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Old 4th Oct 2022, 6:18 pm   #18
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

Ok, so tonight I decided to give a last test a try. I took off slider number 3 the problematic one, and I soldered slider number 1 i it's place. Now the unit doesn't have the issues which should confirm the problem is in the slider itself. The only thing I left not well done was a bit if rust on the brush. I am attaching photos for any notes on your end. I am not too sure if the fader itself might not also be damaged so I have photos of both. Anyway, please share any suggestions while I try to get rid of the rust.
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Old 5th Oct 2022, 9:33 am   #19
sourbiscuits
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Default Re: [HELP] TASCAM Porta 05

So. Upon taking apart the problematic slider, I used the multi meter again. Without the brush ot was reading variable resistance above 100k ohms where the sldier is labeled 50k. My only question left is if the specs of this one are ok considering the original one is labeled 735w? https://www.tme.eu/nl/details/cde23n...s/sr-passives/
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Old 5th Oct 2022, 11:12 am   #20
DMcMahon
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Default Re: [HELP] TASCAM Porta 05

Do not know what the 735w signifies, obviously not 735 Watts.

If the new part mechanically is compatible size wise then a good chance it should be fine.

David
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