Sony TCM-848 Cassette Recorder - Page 1
Forum section: electronics / repair

author: DrG
author_rank: Super Contributor
timestamp: April 24, 2021, 05:07:02 pm
content: I have a TCM-848, purchased ~1990 or so. It is like new, except it doesn't work. As far as I can remember, it never worked. I have a faint recollection that it did not work when I brought it home but I never returned it - probably because I lost the receipt or something like that.I have minimal repair skills, especially mechanical repair skills. The unit, while retro (came out in 1987 I believe), is not particularly valuable. Even for parts only would likely $bay for US$10-20 I would think. I have done some due-diligence and can't locate a service manual other than at a price near what the unit is worth.My hope is that I can get some help with a repair or some advice in that regard.Here are the symptoms...When you insert a known working cassette, it will not play. You can hear a brief and appropriate (e.g., music or data) sound from the speaker and it will 'lurch' but not play and it is not moving the tape. This is exactly what I remember it doing and is what it does now.REW and FF do not move the tape (although you can hear it trying.Cover off with no cassette inserted, the two belts (see below) move freely when PLAY is pressed.I can't say whether they are loose or tight because I have no reference. But, the belts move and do not look like they are slipping at all. From reading, I know that these belts degrade, but, again, the unit did not work when new and with that same symptom, based on memory.The spindles/hubs, not sure of the right nomenclature (see below) move (with no cassette installed) as they 'should' when PLAY, REW or FF is pressed.If a cassette is inserted, those spindles donotmove and, with PLAY, I can sometimes hear some loud squeaking, but not from the speaker. I have not kept it that way for long as I don't want to damage it further.So, what do you think? Can this be fixed easily and by a low-skilled person? What is my next move?

author: andy3055
author_rank: Super Contributor
timestamp: April 24, 2021, 05:46:31 pm
content: While the cover is off like in your 1st picture, try playing a cassette. If you see that the motor pulley is turning but the belts not moving, you can say that the belts are stretched. Give it a nudge and see if you can get it to move. If not, you may need new belts. If those fail, it might be the clutch mechanism under that flywheel (the large pulley). It is also possible that the capstan bearing is gone dry. You can lubricate it with a very tiny bit of Triflow oil (https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=triflow&_sacat=0). Make sure not to get it on the capstan but only in the bush. In any case, you will need to dismantle a few things to see what is stalling it.

author: DrG
author_rank: Super Contributor
timestamp: April 24, 2021, 05:56:23 pm
content: Thanks much for the response.Cover off, like in the 1st pic...cassette inserted...PLAY pressed...belts move freely with no discernible slipping, emits a nice mechanical squeak. Also, hubs (as in 2nd pic) move freely in either direction with power off.You mentioned clutch, can you tell me more?

author: DrG
author_rank: Super Contributor
timestamp: April 24, 2021, 06:58:04 pm
content: I took the ps board off and I see a spring! Just sitting there, just as in the pic. That spring just can't belong there - right? I mean I am not mechanically inclined, but....

author: DrG
author_rank: Super Contributor
timestamp: April 24, 2021, 07:19:39 pm
content: Closer inspection reveals a small washer which was stuck to the component side of the p/s board.These two pieces fit well on top of that gear, but what would hold them in place? They come up against the components? What is going on here and is it related to the problem?

author: DrG
author_rank: Super Contributor
timestamp: April 24, 2021, 07:53:50 pm
content: That spring and washer placed on top of that gear line up well with DIP-> printed on the circuit board.There is no way that they can sit on top of the gear like that...Could that spring and washer be meant to be under the gear? I mean part of the gear mechanism there?

author: DrG
author_rank: Super Contributor
timestamp: April 24, 2021, 08:09:05 pm
content: Looking at this video....at 24.26...is that a spring under the gear?? Is that what is going on here? Did someone just forget to put that spring and washer in the right place?? dayam I wish I had a service manual.

author: DrG
author_rank: Super Contributor
timestamp: April 24, 2021, 08:25:52 pm
content: Hmmm I may be getting closer...This sitehttp://stereo2go.com/forums/threads/walkman-150-clutch-repair.628/has info on Walkman clutch repair and includes this diagram:and also this pic:showing relevant components (different cassette player but, hopefully, there are clutch mechanism similarities that I could make use of).But how do I get under that gear with out bricking the whole thing? Also, how do I get the orientation right - this is where being non-intuitive mechanically is a real liabilityMaybe I should go take a nap and wait for someone to chime in.

author: andy3055
author_rank: Super Contributor
timestamp: April 25, 2021, 12:00:13 am
content: If you look at the very first picture, you can see how the spring is positioned between the board and the second pulley. When you removed the board it had fallen off! The board seems to act like part of the clutch mechanism in this case. I must say I have never seen a thing like that! So, from what I can see, all that makes the clutch mechanism.When you did the test as I mentioned earlier, did you see the large pulley rotating when you had a cassette in? If it does not rotate, but the belt keeps running, it means it is slipping. You will need a new belt then. Also try oiling the capstan, which is the shaft on the other side of this large pulley (actually it is like a flywheel). Also check the pinch roller. Is it free to rotate? Is the surface of the pinch roller looking shiny? If so, it may be hardened and may be not providing sufficient pressure on the tape and pushing it when the capstan rotates. The pinch roller is also spring loaded. Does it have a good pressure against the capstan so that the tape is nicely gripped between them and gets pulled?

author: DrG
author_rank: Super Contributor
timestamp: April 25, 2021, 12:25:27 am
content: Yes, I noticed what you are saying about the first picture and I had not noticed it until I took off the ps board.I know this sounds crazy, but I just can't believe that system, as it is in the first picture is intentional. If it were, I would have been able to simply put pressure at the point that the spring is at and it would rotate the cassette - it did not.Second, there is nothing on the ps board that would support putting enough pressure on the gear. As crazy at it sounds, I think it was just sloppy QC - remember, it never worked when it was brand new.I am too far down the rabbit hole right now to remember the answer to your other question. Sorry.I don't think it is a belt problem and here is why I think that....I have not been able to find the right position to engage the clutch such that the cassette will move - even when I am moving the gear manually.Considering the following components:Also look at a pic from someone else's unit hereand if you read the problem he was having, it is related but differenthttps://www.reddit.com/r/cassetteculture/comments/6kvv9q/sony_tcm848_repair_advice/He has no visible spring (maybe he should have and you are right) but if he puts pressure on the 'black dial', it engages.I don't know where that spring should go but I think I should be able to find a position that will engage the PLAY function, with pressure, and I can't. That white gear has a smaller gear (bad pic) that should engage play...that is what I am thinking...but I am also thinking that I don't know what I am doing, have no manual and should have tossed this in the trash 25 years ago(and thanks for your suggestions and please continue if you can)Edit: what I really want to ask that guy is whether he sees a spring under that black dial! because that would help a lot, but the post is years old.

author: fzabkar
author_rank: Super Contributor
timestamp: April 25, 2021, 12:42:41 am
content: The smaller white disc appears to have a radial crack.

author: DrG
author_rank: Super Contributor
timestamp: April 25, 2021, 12:46:09 am
content: Quote from: fzabkar on April 25, 2021, 12:42:41 amYes it does, I noticed that also and I think it was there from the start.Based on that fellow's pic, the mechanism could look like this:Or the white gear could go the other way around...I might have had a pic of it when I got to that point, but either way...see all that space...seems like a spring would go there - no? A spring there would also be consistent with the Walkman diagram posted earlier.

author: DrG
author_rank: Super Contributor
timestamp: April 25, 2021, 01:07:50 am
content: If you look at the white gear in the previous post...the larger gear (I think that is the drive gear) needs to contact the top gear in the pic below (play is not pressed).The smaller gear needs to contact the lower gear in the pic below (play is pressed).When I manually move the lower gear in the hole, I can see the cassette spindle and tape move, so I think the position of the white gear in the previous pic is in the correct orientation.

author: DrG
author_rank: Super Contributor
timestamp: April 25, 2021, 01:42:36 am
content: I am going to have to call it...Beaten by a 30 year old cassette player...that didn't work when I bought it and decided to stay that way...oh the shame !Hello Amazonhttps://www.amazon.com/QFX-RETRO-39-Shoebox-Recorder-Player/dp/B076W2F1GV/ref=zg_bs_172628_7?_encoding=UTF8&psc=1&refRID=KK2MDZM2S2XS8TK1QPZQ

author: andy3055
author_rank: Super Contributor
timestamp: April 25, 2021, 06:09:00 am
content: Sorry about this. It is difficult to see what is going on with it. If you can put it back the way it was and see what is happening when you press the play button. Not necessary to have power but observe what things are moving and pushing any of the gears in to place to engage.

author: DrG
author_rank: Super Contributor
timestamp: April 25, 2021, 04:06:56 pm
content: Quote from: andy3055 on April 25, 2021, 06:09:00 amNo reason to apologize - sincerely - I appreciate the effort.As I noted, I "called it", meaning it is going to be salvaged for a few parts (nice speaker) and then off to a land fill. While clearly unsuccessful, I don't really feel any shame. I spent an evening on it and did a decent job (in my view) of trying to figure out why the thing never worked and developing a  systematic approach as to how it could be made to work.A service manual would have been mighty useful as would much more skill on my part.My conclusions, and I could be wrong, is that "spring" was never installed correctly and that is why the unit never worked. It had absolutely no function where it was and was exerting almost no pressure on the gear mechanism. In fact, it had just enough to stay in place unless it was toted around a bit - which it never was because once it didn't work, it was placed in a box.The resulting problem was in the alignment of that white two gear piece (drive and clutch gear?) which has to be held in a particular alignment. Not saying I am right, but that is my conclusion. Repairing stuff is a skill, I might not ever get there, but I can improve - so I look at it as a learning experience (how's that for spin?.Now, I would love it if someone had that model and the manual and a lot of skill and could explain it - failing that, it is over

author: andy3055
author_rank: Super Contributor
timestamp: April 25, 2021, 05:34:54 pm
content: BTW, just try this last thing. Expand the spring a little bit by pulling it apart. Put everything as it was and see if that exerts enough pressure to drive the thing.

author: DrG
author_rank: Super Contributor
timestamp: April 25, 2021, 06:15:01 pm
content: Quote from: andy3055 on April 25, 2021, 05:34:54 pmAndy, you are as bad as me - and I mean that as a compliment. Perseverance (not perseveration) has served me well my entire life...it is not OCD, it is looking for challenges and seeing something through. To answer your question, I absolutely tried expanding the spring and in the position originally shown (just under the component side of the ps board - an absolute no go. It did not produce any tangible pressure on the black wiper housing the drive/clutch gears (nor was the PS board warped as far as I could tell). Neither was there a beneficial effect from manually applied pressure. That gear was not aligned properly and it is housed in that sliding arm and if anything is amiss, it gets screwed up - that is my thinking. If that is the design, my vote is thumbs down. But, I also consider that it may simply be a lack of skill on my part, either way...the issue is moot...But look on the bright side, I have; a little more space in a cabinet, a nice speaker, a cool Mabuchi 6v motor (specs and new ones still available), a microphone, a few miscellaneous parts (no caps because you nerds have me fearing that if I use a 30 year old cap, I will put my eye out, and some hardware. All-in-all, a silver lining, of sorts.

author: andy3055
author_rank: Super Contributor
timestamp: April 26, 2021, 01:30:32 am
content: Point of no return, I guess!

author: Dr.error 404
author_rank: Newbie
timestamp: June 22, 2023, 03:55:41 pm
content: So mine can play but it gradually slows down and just stopWhat do I do

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: June 23, 2023, 09:56:53 am
content: manual if it helps for 838 model

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: June 23, 2023, 11:12:11 am
content: https://freeservicemanuals.info/en/servicemanuals/viewmanual/Sony/TCM848/TCM858/listed here but you will need to ask for it