How To Repair Rightside Sound Akai Cassett Deck Model #cs-m01

Akai GX-1900D reel to reel right channel sound problem

Word in 'Tape' started by jdawg, Jul 5, 2022.

I just got an one-time Akai GX1900D reel to reel from my dad. He said he stopped using information technology a long time agone considering the right channel wasn't working. So I hooked information technology up and played some music and simply sound comes out from the left side but on the right side the book is very very low even with the volume for the right channel turned all the way up. So I noticed equally I left information technology on while playing music the volume started to increment but information technology still didn't sound as clear and full compared to the left channel. I accept to turn the right book to the max and lower the left much lower to get both channels level matched. Does anyone know what could be wrong? I downloaded the service manual and took a look at the schematics of the preamp section. I think it might exist a trouble with one of the four 2SC458LG transistors just I can't be sure. I realize this is an old unit but if any aid I can would be much appreciated. But if it turns out its too difficult to repair then possibly its not worth trying to repair.

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--That's southward r2r with a cassette in information technology too, right? I assume the cassette does it likewise?
--could be those transistors - Akai'southward are known for them not to last.
--ever all-time to start with Deoxit, can get the spray at radio shack and spray the pots like those book pots. There are threads on hither nearly doing that.
--if y'all take the faceplate off, check the potmetal cams behind the play and rewind levers. (and a couple deep in the machine normally) They often crumble away and interruption, rendering information technology useless, until you detect some good used ones. Check that before you put much time/money into it.
I'd say you very well may be on the right rails with the transistors. If it was your dad's it may exist more than worthwhile fixing it, thats a neater matter than to go buy 1, I think.
Yeah its the one that also has a cassette player built in. I get the aforementioned problem likewise with playing cassettes. The volume controls seem to work well still and at that place's not static crackling sounds when I adjust them but I'll probably still try to get some Deoxit to clean them once I go around to repairing information technology. I guess I'll go alee and social club some transistors and hopefully replacing them will prepare the problem. I think the 2SC1815 is good replacement from the inquiry i've done. My dad never used it much so I'yard hoping this volition be a decent sounding reel to reel deck if I can get it repaired.
Why are you then sure that the transistors are the cause? Blindly swapping parts with guesswork similar this is expensive and may not even solve the trouble.
Y'all should at to the lowest degree diagnose the problem methodically.
Have you tried recording? Practice both channels work in this mode?

Before yous buy ANYTHING, have the communication given by geartech and utilize contact spray on the internal rec-lead slide switches. piece of work them back and forth about 20 times, and then test. Aforementioned goes for front panel selector switches (reel-cassette mode).

Feed an external source similar a cd or mp3 actor into one of the inputs, see if you lot get audio on both outputs.

Once y'all become going, you may well be surprsed by how simpel the gear up could exist. I changed the capacitors (common failure part , BTW) in the output stages of my Akai not long dorsum, gave it a new lease of life.

Don't assume it'southward something unfixable just however!
I looked at the schematic for the preamp section and took a judge that it might be the transistors. I also thought it could be a capacitor problem too. I tried recording from a cd player and the right channel even so doesn't work that well but I go really good sound out of the left. I have a lot of experience with taking electronic things autonomously and troubleshooting them from the work i do so it shouldn't be too difficult to effort replacing the transistors get-go. I only paid 99 cents for the transistors I demand so if it doesn't gear up the trouble it didn't cost me that much other than my own time. But I will still endeavour doing what was suggested above once I get information technology opened up.

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...It could be a wiring problem, it could exist a switch trouble.... the indicate I'yard making is, until you try to narrow this downwards, you're working on guesswork.Please expand. Does the sound you recorded also play dorsum weakly on a known good machine? Does the CD audio come through the auto's line out weakly?Up to now, as far as I can tell, yous've just worked on a hunch about some transistors! That'due south not troubleshooting in my book.
Accept yous measured any voltages to compare the good channel with the bad? Have you at least desoldered the doubtable transistors and measured the resistance B-East and C-E or checked for shorts?

You're right, transistors are cheap, but it pays in the long term to be systematic. I'm just trying to encourage proficient habits hither!
I figured since it sounds a scrap better afterwards its been warmed up a while it was probably an electronics related trouble. Merely who knows since I"m just guessing so maybe y'all're right and information technology could be another simple problem.
I tried what I recorded on a good record deck and it still sounds bad on the right channel. The audio coming out of the line out is likewise the same when monitoring the CD audio.

You lot're right I haven't actually done any troubleshooting withal since I oasis't had time to open it up to take a expect. I'm notwithstanding going to try removing the transistors to test them with a meter. It's just the transistors were the first affair I thought of only I could be completely wrong on that. I approximate I should have checked the transistors first earlier buying a pack of new ones for 99 cents lol. I don't how much effort I'll put into fixing this thing but hopefully I tin can become it done.
In decks like this, it gives no reason to be systematic, or desolder those buggars and attempt to meassure them - just supersede them on the spot.
I guess I should be more systematic just I will keep that in mind for when I really practise get around to taking a look to see what's incorrect. Hopefully I'll accept some time this week.

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unless you have a signal tracer, and the other tools, in that location is no reason to use too much time to effort to save a buck or 2
being systematic would mean you could follow the bespeak path, and effigy out why things are as they are, then you would repair that faulty role of the circuit. Just to find out that you one week later, or ane month after would experince some sort of flash back. Now another part of the excursion would neglect ????

These AKAI has a problem - they used a transistor with a build in self_destruct function : Corrosion will occour on the leads, and it will non stop at the example, it'll continue within the transistor, and cause information technology to malfunction. Every tech, that ever has touched theese AKAI's know that, and would say : Supercede theese decumbent to fail transistors !! It is not a very clever descition to try to salvage a buck or ii here. nor to save time - the endeavor in taking one out and try to meassure information technology, are amend spend replacing it. The task is in fact easier.
Indeed, Akai was very well known for transistors which loved to get corroded leads. Almost servicers who know this model tend to replace them all. An infamous weakness of the Akai marque.
Im all in favor of existence systematic...just this sounds similar information technology falls into the "while yous take it apart" category...regardless of the bodily repair.
I finally got around to taking a wait inside to see what could exist wrong. Getting to the summit side of the preamp lath to remove components was non easy. I measured the 2SC458 transistors and they all seem expert. I had my meter in diode test mode and I measured from the base of operations to collector and emitter and got a reading around 0.7 and if I measure beyond the emitter and collector I become goose egg which is supposed to be good.
And then then I looked at the schematic and looked at what came later on then I figured it could be the LD3141 op amps. I wish I had a scope so I could measure the outputs and I think that would have been the piece of cake way. In that location'south but 1 for each aqueduct so I was thinking to confirm if information technology is the op amp I could remove them and switch them around and if I become good sound out of the right and then that was the problem. But instead I get no audio at all and as soon as I turn it on the VU meters go the other way and don't move at all when music is playing. I can't figure out why its doing that. I've put the op amps back in their original spot but I still get no audio. I estimate switching them around was a mistake. Possibly this thing isn't worth fixing anymore.

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Peradventure both op amps are now dead (they are known to be unreliable).
Go a length of bare solid wire (~6"). Y'all can use information technology as a point generator. With the deck hooked upwards to an amp and speakers and in play style (no tape), touch the wire to test point 1 (both channels). You should hear a hum/fizz through each speaker (exam both channels). Then go along to test betoken 2. If say you now hear hum from the left aqueduct and not the right, so the op amp is bad. Proceed to examination points iii and iv. The last test point would exist the play head wire. If you impact it, at that place should be hum.

As well, the circled switches/pots could be bad, but I presume you already cleaned them (y'all were told to).

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Last edited: Jul 12, 2022
I did spray the volume pots but it seems electronic stores here don't sell deoxit. Then I used MG Chemicals Contact Cleaner instead just that didn't seem to do anything.
I tried doing what you suggested. I got a 22 gauge solid strand wire to utilize at the test points but I didn't hear anything at all when I touched the output at the op amp on both channels or at any other point earlier that. I made sure the volume pots were adjusted to the maximum too. Then I touched the cassette play head wires and I did make sure that the cassette switch was selected. I didn't hear anything either from touching the head wires. The VU meters simply move all the fashion to the left when I plough it on and I noticed that adjusting the pot for either channel will sometimes brand both meter needles move a bit to the right at the same time to the aforementioned position and so they get back to the left well-nigh position when normally they should exist resting at naught.

I expected to at to the lowest degree hear a buzzing sound so I'yard not sure what the problem is. Maybe both op amps are dead and all I need are new ones.
If you lot put the wire on the input of the IC and got no output and then it is bad. Brand sure the IC is getting it'south DC power supply voltage.
You would need to install another type of IC and do some mods to the lath. The original IC is not available.

http://www.obsoletemedia.com/tapedecks/akai3141/
Cheers for the link on how to mod the board to use another replacement IC. Information technology looks a bit complicated though. I did some searching and constitute a way to brand a replacement op amp that fits int he same nine holes as the original. I just need to order the transistors and resistors to brand the excursion so I promise this works.
http://www.tomjewell.com/Technical/akai/akai.html

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I also saw that link, but I didn't know if you would exist comfy "manufacturing" that tiny printed excursion board equally indicated. If you are, so that'southward good. It's probably the best selection.

Last edited: Jul 14, 2022
I used to compose my own boards a long time ago and I'one thousand used to soldering small smt components so it shouldn't be too hard to make. In one case I go the boards done and installed I'll requite an update to let yous know if it stock-still the trouble or not.

Concluding edited: Jul sixteen, 2022
I fabricated the new op amp pcb'southward and soldered all the components on. I removed the former op amps and soldered in the new ones. I turn the unit on and both vu meters go all the way to the left and then I knew it didn't work and there's still no sound with both cassette and reel. Maybe I need to use Deoxit on the switches and pots instead of the MG Chemicals contact cleaner. Simply the switches and pots announced to be working when tested with a multimeter. Looks like I might have screwed up something else when I switched the original op amps around to confirm if the problem really was a bad op amp in the right channel.