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Cassette Deck Sounds A Bit Flat During Playback

J

jmiles1960

Super Member
Picked up a nice older Technics RS-630 cassette. It sounds a bit "flat" during playback of tapes. I cleaned the heads, but no noticeable change. Ran it side by side with my Akai GXC-725D (cassette deck) and you can tell a slight difference in playback quality; cymbals missing and overall not as "bright" as the Akai. (using same Normal tape settings on both). Maybe technically they are not in same quality league; I don't know...

Any advice on what the Technics might need? Demag? Re-cap the audio section? Playback head worn out? Due to the design of the cabinet, I have not done a close up inspection yet.

Overall, deck is in very nice condition. Would like to give it an audio tune-up if possible, as I enjoy these older style decks.

Thanks in advance for the feedback.
 
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I have only heard of one instance of worn out heads on a cassette deck. I would run my fingernail up and down the rec/pb head and if you nail catches, then it's possible. My guess is you will not feel anything.

Keeping in mind that I have no particular experience with your deck,
I will tell you that I bought a nice Yamaha deck 30 years ago. Recording seemed quite flat, so I took it to a service center. Within 10 minutes they had it sounding great. They said the recording level on the tape was way too high (ie-meters would show peaking around 0 db, while actual level being sent to tape was way too high.) I made many great sounding tapes with that deck. I actually still have it. It sat idle for about 20 years. Now the same symptoms are evident. Perhaps the same drift of level has occurred.

An crude but easy way to test-record some more material at perhaps 6 db down from 0db peaks, no Dolby. Then compare with source upon playback. If the highs are still dull, and hiss is clearly evident, then rec level is probably fine. I would check or have checked, Bias level. Try reducing Bias and test again.

There are many others with more experience here, so please defer to them if they see your post.

Thanks,

Paul
 
I have seen MANY worn permalloy cassette heads, but then, I was in the repair business. Oldvinyldude's tip about seeing if your fingernail will catch in the wear groove is as good as any other test.

Time was, you could buy a credible-quality permalloy cassette head for six to eight dollars, and install it with MANDATORY head re-alignment in a half hour; fifteen minutes if access was easy!

The more costly ferrite heads seldom wore out.

If you are experiencing a problem with tapes that you record yourself, make sure the tape-type selectors are in the proper position for the tape you are using. With a "standard bias" (Type I) tape, if you use the CrO2 (Type II) or the metal tape (Type IV) position, your recording will be overbiased and sound dull. Dolby Noise Reduction makes any such deviation sound worse. Incorrect record bias (too high a bias current, an internal adjustment) will also make a deck's own recordings sound dull; it IS possible to tailor the high frequency record-play response of a cassette deck by tweaking the record bias. Generally the internal recording level sets will have to be recalibrated at the same time because altering record bias also alters record level, and incorrect level will also throw off the operation of Dolby Noise Reduction.

If the problem is ONLY with pre-recorded tapes, the head may be misaligned. This often happened with spring-return cassette transports (the kind where, when you push STOP, the entire pinchroller-head carriage SNAPS back under spring tension); much more seldom with "soft-touch" or solenoid operated types. The spring-return type can jar the head out of alignment, even if lockpaint was used at assembly and in subsequent servicing.

Most of the time a deck won't have head alignment problems on its own tapes. Those using a combination record-play head are perfectly aligned by definition; and most three-head cassette decks have their record and playback heads on a single housing, matched at the factory.
 
Paul - thanks for the info. If you know of anyone in the MD / DC / VA area who works on these, I would be interested in having it checked out.

Brett - thanks for the link. That's the same deck I have. Nice looking deck but the front / angle loading is very mechanical. I probably should have given the purchase more thought and review.

Appreciate the feedback guys.

BTW, Brett, that's one heck of a system you've got!
 
GP49:

I was careful to match the bias and tape settings on both machines. Yes, I notice the lack of "highs" on both pre-recorded cassettes and ones I made when playing them back on the Technics. There is just an edge of the high end that the Technics is not playing back for whatever reason. Missing cymbals, etc... you can easily tell.

Due to the angle of the head / assembly in the transport, I've got to get a dental mirror or pull the case off for closer inspection. Can't assess if it's visably worn or not.

Will post pics and let additional details as I continue to investigate.

Thanks for your feedback. I didn't pay a lot for the deck and probably would rather stick with my Akai-725D (3 head) as the higher quality deck. Picked up the Technics to go with my "Technics system". Just hate to see a nice deck not work to full potential.

Thanks again - Jim
 
Roving: No, actually I have not tried making a recording / playback test. Will do this afternoon and post results. Good suggestion.
 
Your RS630 are using a HPF head (HotPressedFerrite) - i've never seen a worn head of this kind. And yes, a dental mirror is the tool to observe heads on decks like this.

Simple test - make a record, play it again - does it sound dull - if no, you may have a azimut adjustment issue when playing tapes recorded on other decks, or pre-recorded tapes.
 
I had a Technics RS-631 (successor to yours) brand new in 1977-78. First cassette deck I bought. My friend had a Sony TCK5 (same price point) which sounded more musical, clearer highs, more alive, everything you are discussing.

I sent my RS631 to Technics to see if it was in spec. It was. But never did sound as nice as the Sony...sold it and bought the Sony.

It might be you are experiencing a design limitation. FYI - I found mine sounded best with Maxell UDXL1 (normal bias) tapes. A bit more hiss and a bit "brassier" highs than XLII chromes, but more musical and alive. TDK's didn't sound so good either.
 
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I picked up a RS-M18 to match a all silver Technics system I had in the dining room. It was in excellent shape, heads looked ok but man did it sound flat. Later on I bought a RS-M240x which turns out to be an amazing deck, in the same league as my Denon and Sony ES three head decks.
 
jan_stevns said:
Your RS630 are using a HPF head (HotPressedFerrite) - i've never seen a worn head of this kind. And yes, a dental mirror is the tool to observe heads on decks like this.

Simple test - make a record, play it again - does it sound dull - if no, you may have a azimut adjustment issue when playing tapes recorded on other decks, or pre-recorded tapes.
Click to expand...

With ferrite heads you can not really tell if it is worn or not without a very good magnifying glass or better still a microscope. Here are pictures of HPF SONY R2R heads (from the TC-756-2 deck) with almost no HF response left to speak about (and almost no gap left visible on the recording head):

Playback head gap:

PF142_2202B_orig.jpg


Recording head

RF142_2202A_orig01.jpg


Recording head gap:

RF142_2202A_orig02.jpg


Good news is that these heads can be restored to almost "new" condition and could work many more years. Here the gaps of the same 2 heads after I've lapped them:

PF142_2202B_lapped.jpg


RF142_2202A_lapped.jpg


Cheers

Alex
 
very true Alex - HPF heads aren't easy to judge, and i'll risk saying layman can't.

back then we had to take a fight with AKAI and Sony if heads was to be replaced under their so called "lifetime warranty"
 
Thanks for the pics Alex. I found your website via another thread here on AK. Excellent source of recording information.

I did a recording on this deck and it still plays back "muddy", with a noticeable loss of the highs. I don't have the means for an up and close inspection of the heads. For now, this deck is going on the repair shelf.

Thanks again for everyone's feedback. I learned a few things here for sure.
 
jmiles1960 said:
Thanks for the pics Alex. I found your website via another thread here on AK. Excellent source of recording information.

I did a recording on this deck and it still plays back "muddy", with a noticeable loss of the highs. I don't have the means for an up and close inspection of the heads. For now, this deck is going on the repair shelf.

Thanks again for everyone's feedback. I learned a few things here for sure.
Click to expand...

Yes, Alex's pics do show that 'lifetime' heads can have their limitations.

Sorry your Technics does not work well, and with the cost of service (I do not have anyone to suggest either), it makes sense to let it be, given that you have a better unit to use. I would be tempted to keep the unit in the Technics stack/rack, just for visual reasons. No one says you have to actually use it :D But then again, when I see a rack of gear with all their lights and indicators, and I am smitten. Even non fuctioning is OK, as long as I have other pieces that work well. I have 6 other cassette decks. I actually use an Aiwa AD-F810 for recording (seldom), or playback (mostly). I have a non functioning Luxman "suckface" that just looks cool-has these big Lucite back lit buttons :yes: Then, there's the Pioneer CTF1250, which needs belts, and probably a reel motor rebuild-not sure when/if I will get to that, but boy, does it look cool!
 
oldvinyldude said:
An crude but easy way to test-record some more material at perhaps 6 db down from 0db peaks, no Dolby. Then compare with source upon playback. If the highs are still dull, and hiss is clearly evident, then rec level is probably fine. I would check or have checked, Bias level. Try reducing Bias and test again.

There are many others with more experience here, so please defer to them if they see your post.

Thanks,

Paul
Click to expand...

I'd take the level down more for this test. Those nice flat cassette deck specs they used to publish were all made at -20 or even -30 dB. Above that level, high-end rolloff becomes obvious on all cassette decks.

If the record and playback levels aren't correctly calibrated, Dolby tracking error will cause just what the OP is hearing (but so will a dozen other things).
 
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