Neutrik TP401 / MJS401D Service Manual

[Nevada]

Does anybody have a service (or any) manual for the first generation neutrik Audio Tester?

[Richard_S]

Yes, I have an operation manual for the MJS401D. It is too big to attach here. The scan I have done is around 40MByte.

[707dave]

I too would be interested in a copy of the manual, I’ve a TP 401 and information is amazingly difficult to find for these units.

[Richard_S]

Hi. Happy to share a scanned copy of the user manual on DropBox. Just shared with another Dave recently.

[707dave]

Oh yes please - that would be perfect. Thanks D

[AlexMUK]

Hello,

I've been searching high and low for a copy of the user operation manual. I'd be most grateful for a CES to your scanned PDF!.

Thanks in advance,
Alex

[AlexMUK]

Bump...  Sorry for the dead thread resurrection.

I'd still very,very much like a copy of the manual if anyone has access.. there are literally two threads I. The I ternet discussing this, and this is one!

[stevezodiac]

Hi there, could anyone share the link to the scanned PDF for the MJS401D please? 
I have one of these with a fault that I am trying to fix. On power on the meter moves and goes back to the central position but the digital display is blank and none of the keys work - although some of the red LEDS are lit.  However if it is set into Diagnostic mode  - by holding in the Level Key in when powering On - then the word "Diagnostic" is displayed and some of the first 5 keys allow some modes to be selected.  So it appears much of it is working, but not the key scanning or display when not in diagnostic mode.

Any available advice or documentation would be very much appreciated. Thanks

[AlexMUK]

Hi Steve,

Nothing to offer from me, but I'd also like a copy of the service manual and/or user manual. I have a MJS401D that may be in need of calibration, but otherwise seems to work ok. Do you have access to the user manual? if so, could you share?.

I've tried contacting Neutrik T&M in the UK, but didn't get a reply to my request. There are still a few web links to people providing calibration services for the MJS401D, so they may be able to help with the documentation.

From your description, it sounds as though the CPU board is working ok. Check the ribbon cable between the CPU board and front panel - if you're getting into diag mode, then at least some of the key scanning is working ok?.

Please do share any documents you find, and I'll do the same!.

Regards,
Alex

[stevezodiac]

Hi. By a process of elimination I have found that if it is powered on with the complete MD404B Oscillator module removed, the display lights up and the keys work and they select functions - its not perfect but it does appear to work apart from the oscillator.

From scouring the internet this appears to be an optional accessory unit.  Its a complex beast.   https://www.worldradiohistory.com/Archive-All-Audio/Archive-Studio-Sound/80s/Studio-Sound-1984-11.pdf  - page 81 shows the unit without the oscillator module fitted - between the meter and power on/off switch at the right hand side. This link in the new products section shows it WITH the optional Osc unit.  https://www.worldradiohistory.com/Archive-All-BC/Archive-All-Audio/Archive-DB-Magazine/80s/DB-1985-03-04.pdf - Copy and paste the links if necessary.

This is a triple layer module crammed with IC's. I removed the top 2 layer boards (presumably the oscillator sections) and tested with only the base layer connected (module reinstalled) - still no display or functions.  With it removed - display and buttons work.
So possibly the base layer pcb is the cause. It also has a 6502 processor on board.

The base layer is also home to 3 regulator ICs and 3 power transistors plus 5 large wattage carbon resistors. One of them is tucked up next to the heatsink of a small power transistor and its banding is discoloured so its difficult to know what its true value is. The remaining 4 are obvious from their colour codes and they measure as they should. As the fault report was that it was left powered on overnight and had decided to be faulty the next day it does 'smell' of a power supply fault. This board looks like it has its own on board power supply regulation. Maybe when it loses power it ties up the data lines for the rest of the system.
Because this unit is buried inside a metal cage, live fault finding is impossible without an extender board. It would be easier to find dinosaurs than one of those.

If there was a schematic or at least a parts list for the MD404 module it would be helpful... until then I shall keep investigating.

[707dave]

Hi
There’s some diagrams posted on tapeheads.net for the Neutrik TT402A. This is the dual channel version of the TP401, but many of the boards are the same.
The diagrams are there for the Oscillator module, but they are for a later version which doesn’t have the analog psu for the oscillator on the microprocessor / digital board. The analog PSU for the oscillator uses a floating PSU to generate the voltage rails. On the early version the voltage rails are symmetrical. On the later version the floating rails are generated on the back panel PSU board and the rails are not symmetrical. These 2 versions of the oscillator module are NOT interchangeable!  The 2 analog boards are the same which is useful.
The microprocessor card on the oscillator has its own 5v regulator, this uses the same unregulated dc as used by the 5v regulator for the Z80 based front panel processor. The oscillator 6802 processor uses the same 4Mhz clock as the Z80.
I’ve got 2 of these units and I’d love to get a copy of the full manual with lineup information!
Hopefully this helps
Regards
David

[ensai]

Hi there,
It seems I am resurrecting this thread once again! Has anyone had any luck in obtaining a copy of the manual? I would love to get my hands on one as I am thinking of purchasing one of these units in dubious condition.

Thanks,
Ensai

[fredswed]

I would love to get my hands on one as I am thinking of purchasing one of these units in dubious condition.

You are in luck today! I got myself a TT402 some time ago and while it works pretty well it didn't come with manuals. So I have scraped every corner of the net and collected a couple of partial manuals and schematics from the net. However, I was very lucky to get in touch with another owner who has just lent me his copy of the manuals for MJS 401D and I will scan them over the next couple of weeks. It is very extensive so it will take some time to scan it.

The different variants of this instrument (MJS 401, TP401, TT402) are quite similar but not identical. Feel free to pm me with details about what instrument you are considering and what the known issues are. With some luck I might be able to help you with a relevant manual. It is a very competent and easy to use instrument but it is also very complex and compact and I suspect it might be a beast to repair even with a service manual in hand.

[ensai]

My saviour! I will send you a PM shortly. I picked up the unit anyway, mostly out of FOMO given that good test gear is hard to come by where I live. It's a technical projects MJS401D, not sure what vintage as the serial number is completely worn off, but the front panel seems a little different to the pictures I've been able to turn up online.

I know it powers on and can measure its own oscillator, and the rest will have to wait until I have the time to look over it properly. You're probably right that it would be a nasty repair - I found pics of someone's repair (of a TP401) on linkedin of all places and there is a lot crammed in there. All the more reason to want to have a service manual!

Thanks,
Ensai

[fredswed]

Since I've received a few pm:s about the service manual, here's an update:

Scanning is completed but I need a little more time to put it all together. I can't promise a date but rest assured I will post here when it is available for download.