tape deck setup question
Hey all;
I've got a Technics tape deck (RS-B18) that is about 20 years old. I had some problems with intermittent channels (rec and play) and took it apart to see what I could do. I found a cold solder joint in the signal path and resoldered it, which (so far, anyway) has fixed the problem. However, there are a few things I'm wondering about. First, the levels (as indicated on the meters) are lower in playback than record. IOW, if I record a cassette with the levels reading around 0, the tape will play back with the levels at, say -3 or so. It also varies depending on how the noise reduction and bias is set: 1. No Dolby, CrO2 - levels are pretty much the same 2. Dolby B, Cr02 - levels slightly lower on playback 3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback 4. any or no noise reduction, Metal - no playback at all (this has been a problem since I got the deck) I can post more combinations if need be, but I hope that this will give the general idea. I also cannot remember if this was the way things were going before the repair (I think it was though). Are these type of discrepencies normal, or can/should I adjust things to equal them out? I also noticed that the playback was a little dull after the repair (to be honest, I hadn't used the deck in quite a while, so it may be the way it always sounded). Would this be a bias setting that I may have inadvertently moved while repairing? or perhaps it needs some adjustment in another area? Thanks |
I would suggest to demagnetize and clean the heads before going
farther. Also, use a tape cassette that is not very old. After these cassettes are a number of years old, the permability of the magnetic coating may deteriate with age. When these decks are calibrated, a proper test reference tape is used to align the playback first. Then for the record section we use a know standard type fresh high quality recording tape, and an audio generator to reference the response of the machine. There is a test reference tape for dolby, and one for no dolby. There are also test reference tapes for metal, and ones for the different types of oxide tapes. For properly setting up an audio tape machine you will need a scope, audio generator, reference standards tape, a high quality recording tape if each type that the machine is supposed to use, and a VU meter. The service manual should have the details of how to set the machine up. There is the combination of the capston speed, tape tension, azmuth, head height, head postion, guide adjustments, pinch roller pressure, and then the adjusting pots for the EQ's, levels, and Bias settings to be set up. This is just to mention a few things that can effect the performance of your audio tape machine. In the lower cost machines they average out many of the adjustments, for the different types of tapes to be used. If the sound is not distorted, or is not out of ballance, and it is uniform, I would just do a head cleaning and demagnetization. I would not venture in to the alignment of the unit, unless I was prepared to go all the way with proper servicing, and the proper checks. You can probably find a head demagnetizer at most audio HiFi stores. Radio Shack used to sell them. You can use some rubbing alcohol and a soft tissue to clean the heads. Most of the non factory authorized shops may have some type of test reference tape and an audio generator, and do a simplified alignment with the scope. This is not going to be a truely accurate alignment. Considering the age and the value of your machine, is this all worth it. Also, the performance of the machine may not be very stable unless it is a very expensive unit, and there are no parts inside that have become off specs from age. Before doing any adjustments, it is very important that the electronics, and the mechanics of the machine are working as best as possible to specifications. If not, and you start to make adjustments, the situation can be made worse. Jerry G. ======== "tempus fugit" wrote in message ... Hey all; I've got a Technics tape deck (RS-B18) that is about 20 years old. I had some problems with intermittent channels (rec and play) and took it apart to see what I could do. I found a cold solder joint in the signal path and resoldered it, which (so far, anyway) has fixed the problem. However, there are a few things I'm wondering about. First, the levels (as indicated on the meters) are lower in playback than record. IOW, if I record a cassette with the levels reading around 0, the tape will play back with the levels at, say -3 or so. It also varies depending on how the noise reduction and bias is set: 1. No Dolby, CrO2 - levels are pretty much the same 2. Dolby B, Cr02 - levels slightly lower on playback 3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback 4. any or no noise reduction, Metal - no playback at all (this has been a problem since I got the deck) I can post more combinations if need be, but I hope that this will give the general idea. I also cannot remember if this was the way things were going before the repair (I think it was though). Are these type of discrepencies normal, or can/should I adjust things to equal them out? I also noticed that the playback was a little dull after the repair (to be honest, I hadn't used the deck in quite a while, so it may be the way it always sounded). Would this be a bias setting that I may have inadvertently moved while repairing? or perhaps it needs some adjustment in another area? Thanks |
ouch
Thanks for the info Jerry. I have demagnetized and cleaned the heads a few times (this was the first thing I did when the left channel was weak), so unless the heads are worn (which is altogether possible) I don't think that's the issue. Everything is fairly well balanced now, so maybe I'll just leave it be. As you pointed out, the deck is quite old, and was only a few hundred bucks when I got it, so it's not like it's a high end deck. I just thought if the calibration process (or some of it) wasn't too involved, I'd see what I could do. "Jerry Greenberg" wrote in message m... I would suggest to demagnetize and clean the heads before going farther. Also, use a tape cassette that is not very old. After these cassettes are a number of years old, the permability of the magnetic coating may deteriate with age. When these decks are calibrated, a proper test reference tape is used to align the playback first. Then for the record section we use a know standard type fresh high quality recording tape, and an audio generator to reference the response of the machine. There is a test reference tape for dolby, and one for no dolby. There are also test reference tapes for metal, and ones for the different types of oxide tapes. For properly setting up an audio tape machine you will need a scope, audio generator, reference standards tape, a high quality recording tape if each type that the machine is supposed to use, and a VU meter. The service manual should have the details of how to set the machine up. There is the combination of the capston speed, tape tension, azmuth, head height, head postion, guide adjustments, pinch roller pressure, and then the adjusting pots for the EQ's, levels, and Bias settings to be set up. This is just to mention a few things that can effect the performance of your audio tape machine. In the lower cost machines they average out many of the adjustments, for the different types of tapes to be used. If the sound is not distorted, or is not out of ballance, and it is uniform, I would just do a head cleaning and demagnetization. I would not venture in to the alignment of the unit, unless I was prepared to go all the way with proper servicing, and the proper checks. You can probably find a head demagnetizer at most audio HiFi stores. Radio Shack used to sell them. You can use some rubbing alcohol and a soft tissue to clean the heads. Most of the non factory authorized shops may have some type of test reference tape and an audio generator, and do a simplified alignment with the scope. This is not going to be a truely accurate alignment. Considering the age and the value of your machine, is this all worth it. Also, the performance of the machine may not be very stable unless it is a very expensive unit, and there are no parts inside that have become off specs from age. Before doing any adjustments, it is very important that the electronics, and the mechanics of the machine are working as best as possible to specifications. If not, and you start to make adjustments, the situation can be made worse. Jerry G. ======== "tempus fugit" wrote in message ... Hey all; I've got a Technics tape deck (RS-B18) that is about 20 years old. I had some problems with intermittent channels (rec and play) and took it apart to see what I could do. I found a cold solder joint in the signal path and resoldered it, which (so far, anyway) has fixed the problem. However, there are a few things I'm wondering about. First, the levels (as indicated on the meters) are lower in playback than record. IOW, if I record a cassette with the levels reading around 0, the tape will play back with the levels at, say -3 or so. It also varies depending on how the noise reduction and bias is set: 1. No Dolby, CrO2 - levels are pretty much the same 2. Dolby B, Cr02 - levels slightly lower on playback 3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback 4. any or no noise reduction, Metal - no playback at all (this has been a problem since I got the deck) I can post more combinations if need be, but I hope that this will give the general idea. I also cannot remember if this was the way things were going before the repair (I think it was though). Are these type of discrepencies normal, or can/should I adjust things to equal them out? I also noticed that the playback was a little dull after the repair (to be honest, I hadn't used the deck in quite a while, so it may be the way it always sounded). Would this be a bias setting that I may have inadvertently moved while repairing? or perhaps it needs some adjustment in another area? Thanks |
"tempus fugit" wrote in message ...
Hey all; I've got a Technics tape deck (RS-B18) that is about 20 years old. I had some problems with intermittent channels (rec and play) and took it apart to see what I could do. I found a cold solder joint in the signal path and resoldered it, which (so far, anyway) has fixed the problem. However, there are a few things I'm wondering about. First, the levels (as indicated on the meters) are lower in playback than record. IOW, if I record a cassette with the levels reading around 0, the tape will play back with the levels at, say -3 or so. It also varies depending on how the noise reduction and bias is set: 1. No Dolby, CrO2 - levels are pretty much the same 2. Dolby B, Cr02 - levels slightly lower on playback 3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback 4. any or no noise reduction, Metal - no playback at all (this has been a problem since I got the deck) I can post more combinations if need be, but I hope that this will give the general idea. I also cannot remember if this was the way things were going before the repair (I think it was though). Are these type of discrepencies normal, or can/should I adjust things to equal them out? I also noticed that the playback was a little dull after the repair (to be honest, I hadn't used the deck in quite a while, so it may be the way it always sounded). Would this be a bias setting that I may have inadvertently moved while repairing? or perhaps it needs some adjustment in another area? Thanks I sympathise with all the above, but when all's said and done we are talking about a 20 year old machine using a format which is rapidly growing obsolete. there must come a point at which one asks: is this worth spending time and money on? Second hand markets are full of cassette decks, even hi-spec ones, going for ridiculously low prices (seeing as CD-R has occupied the mainstream for home recording.) Rather than spend time on your present machine which will possibly need a schematic and test equipment to rectify completely, it may be simpler to get a decent , tested, quality 3 head machine from a reputable dealer if you really want a good spec cassette machine. Ben |
Thanks Ben.
Rather than spend time on your present machine which will possibly need a schematic and test equipment to rectify completely, it may be simpler to get a decent , tested, quality 3 head machine from a reputable dealer if you really want a good spec cassette machine. Ya, I know that, but I hate to throw something away that I might be able to fix (it's a little "problem" I have). Also, if I can do it, it would be cool to learn how, especially in light of your above comment - if I screw something up irreparably, I can always pick up a used cheapie (hell, I've pulled decks out of the garbage that were working fine), and I have another one lying around anyway. "b" wrote in message om... "tempus fugit" wrote in message ... Hey all; I've got a Technics tape deck (RS-B18) that is about 20 years old. I had some problems with intermittent channels (rec and play) and took it apart to see what I could do. I found a cold solder joint in the signal path and resoldered it, which (so far, anyway) has fixed the problem. However, there are a few things I'm wondering about. First, the levels (as indicated on the meters) are lower in playback than record. IOW, if I record a cassette with the levels reading around 0, the tape will play back with the levels at, say -3 or so. It also varies depending on how the noise reduction and bias is set: 1. No Dolby, CrO2 - levels are pretty much the same 2. Dolby B, Cr02 - levels slightly lower on playback 3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback 4. any or no noise reduction, Metal - no playback at all (this has been a problem since I got the deck) I can post more combinations if need be, but I hope that this will give the general idea. I also cannot remember if this was the way things were going before the repair (I think it was though). Are these type of discrepencies normal, or can/should I adjust things to equal them out? I also noticed that the playback was a little dull after the repair (to be honest, I hadn't used the deck in quite a while, so it may be the way it always sounded). Would this be a bias setting that I may have inadvertently moved while repairing? or perhaps it needs some adjustment in another area? Thanks I sympathise with all the above, but when all's said and done we are talking about a 20 year old machine using a format which is rapidly growing obsolete. there must come a point at which one asks: is this worth spending time and money on? Second hand markets are full of cassette decks, even hi-spec ones, going for ridiculously low prices (seeing as CD-R has occupied the mainstream for home recording.) Rather than spend time on your present machine which will possibly need a schematic and test equipment to rectify completely, it may be simpler to get a decent , tested, quality 3 head machine from a reputable dealer if you really want a good spec cassette machine. Ben --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.775 / Virus Database: 522 - Release Date: 08/10/2004 |
On Sat, 23 Oct 2004 10:17:57 -0400, "tempus fugit"
wrote: Hey all; I've got a Technics tape deck (RS-B18) that is about 20 years old. I had some problems with intermittent channels (rec and play) and took it apart to see what I could do. I found a cold solder joint in the signal path and resoldered it, which (so far, anyway) has fixed the problem. However, there are a few things I'm wondering about. First, the levels (as indicated on the meters) are lower in playback than record. IOW, if I record a cassette with the levels reading around 0, the tape will play back with the levels at, say -3 or so. It also varies depending on how the noise reduction and bias is set: 1. No Dolby, CrO2 - levels are pretty much the same 2. Dolby B, Cr02 - levels slightly lower on playback 3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback 4. any or no noise reduction, Metal - no playback at all (this has been a problem since I got the deck) I can post more combinations if need be, but I hope that this will give the general idea. I also cannot remember if this was the way things were going before the repair (I think it was though). Are these type of discrepencies normal, or can/should I adjust things to equal them out? I also noticed that the playback was a little dull after the repair (to be honest, I hadn't used the deck in quite a while, so it may be the way it always sounded). Would this be a bias setting that I may have inadvertently moved while repairing? or perhaps it needs some adjustment in another area? Thanks It's perfectly normal for you to lose a bit of gain. Meters are far from exact and you are dealing with an analog process. Tape formulations are such that they are simply not 100% capable of capturing all the signal that you give them. That's why you run a test recording before the real thing on any type/batch of tape you're going to use. Also has alot to do with the type of metering you're using too. Some decks use A weighted some B or even C. Some use a average weight combination etc... (Peak, Average and mixed are the 3 basic flavors tho' there are dozens of variations.) In fact it's desireable to stay a bit under 0 with most tapes, especially Chrome and Metal, both of which distort easily with oversaturation. As for DBX, it's designed to under record about -3 to -10 dbs to allow for greater headroom on high or sudden peaks/surges. There wer attempts in the late70's early 80's to design cassette decks that would test tone tapes and set the optimum level. One was the Luxman KXP-102, I had one of these and they produced the most accurate, clean mids and lows capable out of cassette tapes. It would run a test tone in three basic ranges(low, mids and highs) and read the results repeating the tones until the optimumlevel had been achieved in each zone. This allowed it to tweak bias and noise reduction until you got the perfect recording with each tape.(It was less than perfect in capturing the very highs but was a great deck for instrumental jass and blues etc...) Just run a test on whatever type of tape you're using adjusting the gain untill you get the desired level that gives you highest sound level without oversaturation.(Think you'll find that you'll be setting the gain around 7 or so and depending on your type of meters the signal will show to be around +2 to +4 during record and bang on 0 on playback. |
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