kgallen

That's very much over-over-stating my contribution. Mostly I've been a sympathetic but largely impotent ear. No Service Manual for the thing that I can dig through... @sfbp is probably a bit mad at me for all of the chatter above, but then I can easily look at a SM for the 940 and thus chip in repeatedly with a modicum of usable input.

No they don't. Consider the MDS-E12 and MDS-E10 as a MDS-JB940 in rack mount format. Ok the I/O is different and there is the SCMS stuff, plus some other features in the setup menu, but under the hood audio wise they are pretty much a 940. There, that's calmed your nerves a bit now hasn't it! Means you won't go looking for an E10 or E12 on eBay! 😄

Don’t start me off!!! I thence started looking at 930 and then 920. Fortunately they are all way too expensive at the moment. I must resist putting a notify search in place… Hmmm good question, not sure I do have a fully working 7a in ‘stock’. The one in the 440 has some intermittent issue. I do have a NOS 7AX2 though and I notice they are no longer available on AliExpress… Love the story on the 930 @M1JWR, fab catch! @BearBoy I’m brain synching with you to resist a purchase!

I wanna know where you see these sub-100 940's. I rarely see one sub-200 these days! However, no, no, no, I'm not looking... I'm not. No.

The primary side winding will have a higher resistance than the secondary. Maybe it’s above what your continuity meter allows - unless you have an ohmmeter as you gave numbers for the diodes. Worth having a look at the removed transformer again. You’re just looking between pins 1 and 4 (which I would presume are the outer ones if they populated all 4). The relay would only affect coming out of standby into full powered up (since it switches mains into the big transformer). But excellent news you have it working, great stuff!!!

Sounds like the primary is bu**ered then! I had that on one of my MDS-E10 that had been abused.

To clarify no continuity between primary and secondary is good and essential for safety and operation no continuity of primary or secondary windings is definitely not a good thing - no operation

A transformer should *NOT* have continuity from the primary to the secondary. That is their main attribute for isolation. If it smells funny and you have continuity from the primary to secondary then I would agree with you that the transformer has been burned by some suspect mains (UK mains applied to a US/CND/JP transformer being typical). Note it needs to really smell funny/acrid. Transformers usually smell a little bit weird so there needs to be a significant acrid smell to suggest it's damaged. On that standby transformer, the primary and secondary windings come out on opposite sides of the bobbin. So with the power OFF you should find continuity (some low resistance) between the 3 pins on the primary side (this is the side nearest the left edge of the PCB). You should also find continuity between the two pins on the secondary side (this to the "inside" of the PCB). This transformer only has a single secondary winding - one coil of wire, the two pins being each end of that winding wire. This is the schematic I'm on about. In this post, transformer T900 is what I'm referring to.

Looking more, that 4 pin IC902 regulator only kicks in with the main transformer. Also from that photo above looks like some of the small transistors have different refdes to the schematics. Those two TO220 trannies to the right of the relay (black rectangle) should be Q904 and Q901 but on the photo I’m sure I can read Q932. That one I recon is Q901 on the schematic since the other one has the 100uF cap and zener diode near it so that would be the discrete 3.3V reg. I’d have a look around those ‘green’ diodes near the main input connector. They are the standby supply bridge rectifier. With power disconnected check none are short or open circuit (should drop around 0.6V when forward biased). You can poke on their legs from above. I agree the IC400 multi-rail regulator is on for standby but since this is on the main board and you swapped the relay board and got the machine working I conclude IC400 is working ok and in the failed machine it’s just not getting any power from the faulty relay board. So initially I would focus on T900 (standby transformer), D904/5/6/7 (bridge rectifier) and C401 (10000uF smoothing cap). That’s all there is to the standby power supply on the relay board (regards power towards IC400). On IC400 you could see if there is about 7V dc on pin 7. Also check there is something on pin 2 (schematics say 2.4V, but it will be very lumpy as it’s just half wave rectified ac, not smoothed).

Hi John You said the standby led wasn’t on so I'd work through the standby power supply (the small transformer) against the schematic. You can do some buzzing out (and checking for opens and shorts) with they unit unplugged. Then you’ll need power to check voltages. I see +3.3V for the standby DC rail, so I’d check for that first. That gets used to enable the relay that puts mains into the main transformer to awaken the whole deck. I don’t think I saw a +5V rail for standby but I’ll check again (on a proper computer rather than a phone!). Of course there are 5V rails when the machine is alive but since you said standby wasn’t coming up I’d start there. Of course apologies if you already know all this, you’re hardly a first-timer! But the good thing is hopefully this is just a simple fault then another great 940 comes alive!

Which regulator John, IC902? Checked all the rails? 5V, 3.3V etc? See if 3.3V out of Q904 emitter which is the ‘standby’ regulator. Ie is the standby PSU rail ok. Then maybe have a look at the base and collector of Q902 to see if that turns on. That switches the relay.

Sounds good! No active components on the relay board is there? (I should check the schematics before waffling on…!). Great you narrowed it down and the rest of the machine seems to be working now you’ve cleaned it up. Great work!!!

Wish you well @M1JWR I hope you get the beauty working. Here if you need me!

Hi Petter, What is the problem you're trying to solve? What do you mean by a "new CPU". Which processor in the device are you actually after? There will be a microcontroller on the main board (usually some Mitsubishi embedded control processor) but in the audio chain, the ATRAC processor (the CXD2664 in the case of the 980) is on the PCB that is part of the drive unit - the way to "replace" this processor is to replace the drive with one from another machine. Neither chip in of themselves will be user-replaceable even if they could be sourced, because specialised equipment will be required. Also the control CPU will have firmware programmed in to it. If you bought a new one it would be blank and I don't know where you would source the firmware image from and again you would require programming equipment specific to this processor. Ergo, unless I'm misunderstanding your intentions, replacing "the CPU" is not really a practical proposition unless you swap the PCB on which it is mounted.

I just watched your videos (thanks!). I'm still tempted to think that disc detection microswitch is not happy. Did you replace the switch or "rectify" the activation pressure on the switch? I think I'd look at that switch again as otherwise your machine looks happy. (Although on first watching I thought the load was a bit sluggish but it does at least look smooth).

(Replied on Tapeheads - any one else fancy a bash at this one?)

Mike Lindup Changes2 CD just arrived in the post, so a little SP dub job for my MXD-D4 today… …yes I am sad and try to match the MD colour to the album artwork! https://mikelindup-official.bandcamp.com/album/changes-2

We’ll that’s it. With gay abandon I’ve thrown caution and OCD to the wind. I actually opened one of my new MDW80T. Just went right out and ripped off the plastic. You don’t know how hard that was. I’ll go to almost any lengths to not open a brand new-new disc. No I don’t know why either. I just didn’t have another new Sony 80 to open and I didn’t want to use a pre-used one. Well I just bought a couple of new-unopened Kraftwerk CDs and I just wanted a Sony 80 minuter to put two of them on in SP. So that’s it, I’ve broke by karma. I’ll be ripping them open now like there’s no tomorrow.

You don't need to put a disc in the machine. Just turn it on and hit RECORD then it goes into "monitor" mode. If you have the input selected as "Analog" then the display will show "AD - DA" (if the input is coax or optical, then it will say "- DA"). ATRAC conversion only relates to data going to the disc. If you're using the machine like this as an ADC, then the digital out is just a straight conversion of the analogue in. Conversely you can use it as a DAC with headphone amplifier (like I do with mine, attached to a PC), select Coax or Optical and hit RECORD, the display will show "- DA". Good luck!

It does now! I think I ran out of characters in that field, so had to prune some info! Believe me, @BearBoy, you are fully implicated (one way or another!) in the 940 and 770 purchases let me tell you! 🤣 940 was from @M1JWR last year and 770 was part of that Control-A1 investigation "we" were doing, probably around lockdown... Nothing new MD-wise in recent times other than maybe a batch of used disks a few months back... (still resisting breaking into many of those new-new ones, how about you?!)

I'd say my 520 requires a *tiny* bit more force than the 940 or 770 to trigger the grab-and-pull but there's very little in it. Whilst the MDM7 uses a belt to actually do the moving, I suspect the "trigger pressure" of pressing the disc into the mech to get it to activate has a lot of similarities in both mechs. I guess on the MDM3/MDM5 you might just come up against the resistance of the gear train in the case of those mechs. Do a bunch of disc inserts/ejects to get the mech moving again and see how you get on. Don't have anything earlier than my 520 to try (otherwise which deck would you like me to try? 🤣)

Yea I had a read through the manual and I couldn’t find Tape Monitor or similar function.

Welcome back! You might want to consider this thread if you’re needing lots of new (new) minidiscs (discs) 🙂

Yes but you’ve got to add gain somewhere. If you can’t do it at the source you’ll have to do it at the MD. The intrinsic noise and relatively limited fidelity of the FM transmitter will absolutely swamp any noise you’ll add at the MD with +8dB. ^^^^ wot the boss says. Enjoy your radio broadcasts and your MD, you’re in good hands.

Does the tuner sound quiet through the speakers on the amp too at your usual volume knob setting, compared to your other sources (CD/tape/vinyl)? It's fairly common for me to need to add some gain at the MD end and it's not uncommon to need +6dB or more, although usually I'm using coax or optical input.