Tascam 244 freq response problem Ch 4

Findlay

Member
A few weeks ago I noticed that channel 4 on my 244 seemed a bit odd. I had to replace the fuses again for the playback amps and on playing the test tape I made in '82 found the high freq playback response way down. Less than -20dB for a 0dB recording from 20 kHz to 1kHz, then 0dB until 125Hz then -7db and less than -20dB thereafter. On all the other channels flat within 2dB from 16k to 25Hz -as was the case for channel four until now. Does anyone have any ideas what could have happened? Maybe it is a head wear effect. Apologies if I can't reply quickly as I wil be on the road for a while over the next week. Grateful for any help, as always!
 
First thing I'd check is that the heads are really clean - the edge tracks are usually the worst with a dirty head. I would also check that the head hasn't become magnetised. If the problem with the machine caused DC to flow through the head then it could have magnetised the head. This would also have damaged your test tape (which is why you should always demagnetise the heads before running a test tape through the machine).
 
A few weeks ago I noticed that channel 4 on my 244 seemed a bit odd. I had to replace the fuses again for the playback amps and on playing the test tape I made in '82 found the high freq playback response way down. Less than -20dB for a 0dB recording from 20 kHz to 1kHz, then 0dB until 125Hz then -7db and less than -20dB thereafter. On all the other channels flat within 2dB from 16k to 25Hz -as was the case for channel four until now. Does anyone have any ideas what could have happened? Maybe it is a head wear effect. Apologies if I can't reply quickly as I wil be on the road for a while over the next week. Grateful for any help, as always!

Does the 244 has any internal equalisation pots for the individual channels?
i suppose it does and worth checking
 
Thanks for your suggestions guys. The head is clean but I will demagnetise it! I never thought only one channel could suffer from magnetisation - and so badly- and the rest remain ok. the test tape still works fine on channel 4 on both my other 244s.I have tried adjusting the playback eq but no real change.
 
I never thought only one channel could suffer from magnetisation - and so badly- and the rest remain ok.

No - I wouldn't expect one channel to be really bad and the rest totally OK but demagnetising is something that is worth doing occasionally anyway.
 
The tape will wear a groove in the head the width of the tape.The tape can skew out of the groove and cause poor freq.response.If you run your fingernail on the head you can feel the groove if it's there.
 
The odd thing is that bass response is way down too. I am wondering if some components have blown. Maybe a capacitor or two? Will try the demagnetise and fingernail check asap.
 
As I know you are all losing sleep over this (to quote Level Anything in his recent post!) I thought I'd update. Got back home yesterday and demagnetised the head. No effect. Fingernail test didn't reveal any major head wear. Got playing around inside and found the channel 4 eq pot is playing up - sort of knife edge trying to adjust it and only getting output in two spots. I guess I'll need to replace it - maybe this is the cause of the problem?
 
Thanks for the replies guys. Hi Level Anything - I tried adjusting the Channel 4 playback eq trimmer pot the one inside the machine near the playback level trimmers - I just turned it a fraction and lost all output on C4. I only managed to get the signal back by turning the trimmer all the back and forwards and pushing on the wiper a little - it only seems to allow signal through a two points of travel so is bound to be set wrongly. James - I tried switch cleaner but that didn't help - I guess it is badly worn. I don't think the pot alone is causing all the problems though as I think it only trims by a few dB.
 
I reflowed the solder joints but didn't check for cracked traces - thanks Sweetbeats, I'll check next time I get home to the machine.
 
Okay. Make sure you have something to magnify what you are looking at...I like to use a 10x jeweler’s loupe, and really good light...and even then sometimes you can’t see the fault. Also, if the signal is intermittent when you are tweaking the trimmer it’s totally possible the wipers aren’t making good contact. I’ve dealt with this in linear pots (faders) where the metal wiper has fatigued and needs to be gently tweaked to make better contact...can’t reasonably donthat with one of those little trimmers. I’d replace it.
 
The channel 4 head will give decreased level at all frequencies due to either extreme wear or that the tape you are using is well worn and the edges are the first to go. Try a new XL II tape in the deck first.
The heads and that means all of them do not test with a fingernail test- that is the stupidest thing I have come across and it tells you nothing.

The way to determine if a head is work is in bright light you see if the surface is flat or rippled. If rippled then it might be ready for a new head.
I would not mess with controls in the unit unless you have the appropriate equipment to put them back where they are suppose to be like the MXT356 or MXT216. Touching things by abstract methods of adjustment have never turned out a good result.
I still work on these in my shop and have new heads.

First trimmers can be sprayed with Deoxit and they are not often failed to need replacement. If you do you can get 6mm Cermet trimmers from Mouser. I don't recall having to replace any trimmers for many years- I have probably serviced 150 of those units at least.
 
Do 4-track heads really get wear like reel to reel? I've never had any tape wear problems on any of my machines, even the ones I used constantly before even knowing we were supposed to be cleaning the transport. I figured the slow tape speed wouldn't do that, and if it did it would take tons and tons of use and the way Findlay has described his machine sounded like it was pretty low hours.

Findaly, do you think that changing your 244 to take type I tape and subsequently using the Maxell UR maybe wore the heads down like he says?
 
Thanks for the replies guys.

Hi Level Anything - I did have a huge head wear problem with my original 244 that I bought in October '82. After about a year the freq response dropped on all the channels. I took it to a local Tascam dealer for repair and they couldn't fix it - I eventually sent it to Tascam head office in the UK. They said it need a new head, for which they were going to charge a few hundred £. I had to argue a bit, saying that one didn't expect this sort of thing just out of the guarantee period with high end gear and they finally caved in, admitting that the early 244s had been made with soft heads and that they had changed the design and would fit one of the new heads for free.

It is this same machine that I've got the problem on C4 with. I haven't used it wth type 1 - I modified another machine I bought off Ebay for that. I looked at the head close up and it doesn't seeem to be showing wear - I'll try to take a close up photo some time to check. I'm pretty sure it is the playback eq trimmer that is playing up - found out from the manual that it is a 100K variable, so I will replace it as soon as I can.

Thanks Skywave - I'll have to take a close up photo of the head to check if it is rippled. The trimmer is definitely shot though. I can't work out from the circuit diagram what sort of effec this would have but it seems pretty catastophic for frequencies above 10K and below 100K.
 
That's so cool that you have a Tascam headquarters that actually can offer some type of service. I've never had any luck with the one here in the states, and I heard that it may have closed. Anyways, good luck with the trimmer. Keep us posted
 
That's so cool that you have a Tascam headquarters that actually can offer some type of service. I've never had any luck with the one here in the states, and I heard that it may have closed. Anyways, good luck with the trimmer. Keep us posted

No idea what your consumer law is like L.A. but in UK it is pretty tough IF you know how to apply it. I would suggest those heads were deemed to be of "Not reasonable merchantable quality" and Tascam UK took legal advice and found they were up a river of excrement without means of manual propulsion and decided to keep the goodwill!

Dave.
 
I realise you are all losing sleep over this still, so I thought I'd put you out of your misery!

I replaced the Channel eq trimmer yesterday - and what a result! The volume shot back to normal levels and the frequency response is perfect - just 2dB down at 18kHz and 40Hz at 0dB record. I still can't work out how the recording response has got back to normal as the trimmer is on the playback board - but it has! Did a quick recording and am still astounded at the sound this 36 year old machine can produce. Thanks for the interest and help guys.
 
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