Author Topic: EEVblog #619 - Dumpster Dive PABX Teardown  (Read 9474 times)

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Offline TVman

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #1 on: May 22, 2014, 05:32:20 am »
Umm, Dave?

This video says it's private and I can't watch it. |O

Can you fix this please?


Thanks,
Hunor

EDIT: it's fixed!
« Last Edit: May 22, 2014, 03:22:00 pm by TVman »
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Online NiHaoMike

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #2 on: May 22, 2014, 03:07:17 pm »
The PSU is definitely a linear type with that big transformer, though the regulators could be switching. Also interesting is that they had two mains transformers in one of the units, probably since they needed two vastly different voltage rails (or groups of voltage rails) and decided to use two off the shelf transformers instead of ordering custom transformers.
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Offline JoeMuc2013

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #3 on: May 22, 2014, 04:00:51 pm »
Hey Dave,

nice teardown once again. Please keep us posted about the outcome of hooking up that hard disk drive to a PC.
About the file system: I'd guess it is a Linux-style ext2, ext, or hpfs file system if Windows cannot deal with the partitions right away.
Thank you!

Regards,
Joe
 

Offline German_EE

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #4 on: May 22, 2014, 08:28:00 pm »
The high-voltage protection on the outgoing lines isn't just to do with lightning, it also stops 220V appearing on a line in the event of an equipment fault. If you're a telecom engineer standing in a manhole full of water the last thing you want to do is touch a live wire.

Also, the neon bulbs are probably to indicate incoming ringing. The normal specification called for -48V DC on the line with 90 VAC over the top of this as a ring signal.
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Offline SeanB

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #5 on: May 23, 2014, 01:27:47 am »
Telecom guys here are very used to getting belted by phone lines. There are a lot of older areas where the copper wiring went past capacity, and they used multichannel extenders to get either 2, 4, 8 or 16 POTS lines running off a single twisted pair with the required power being line derived. Thus you find a single pair in a trunk cable or inside a building having either 160, 200 or 250VDC on it, and no marking that it is high voltage. The paper cabling definitely gets unhappy with this with time, as often you will find a fault where the joint end has burned back about 2m from the insulation failing if moisture got in. I had to put in a new cable conduit, as the existing cable was both failing and refused to come out of the steel conduit in the concrete. Had the Telco dig up the street to the joint, then they laid the new underground cable and I provided the new external conduit up  a floor to get the cable to a wall riser. then it was terminated and went back down again to get to the original MDF.
 

Offline nitro2k01

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #6 on: May 23, 2014, 01:55:08 am »
What's fil1 on the oscillator board? (Around the 8:15 mark.) A passive filter?
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Offline hikariuk

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #7 on: May 23, 2014, 07:06:09 am »
I wouldn't be surprised if the disk is formatted using one of the FAT variants, even if it's not using a Windows based OS.  They're old and pretty ubiquitous.  Even Atari STs could read FAT12 formatted floppies out of the box, afaicr.
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Offline magiccow

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #8 on: May 23, 2014, 11:14:14 am »
The MT8952B will probably be for decoding the signalling (D channel) for the upstream link, e.g. ISDN or Primary Rate.
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Offline Khashoggi

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #9 on: May 23, 2014, 07:03:17 pm »
I had a TVS-200 the bigger cousin to that voicemail system. It also used a hard drive.

The drives would eventually fail, and backing up a copy was helpful. I used dd to make a file backup of the whole drive.

The drives contained the voicemail files and prompt files (audio you recorded to be used as custom labels like "press-1 for sales" etc...)

As I recall it was formatted fat-16 and was readable and had a folder structure.

The voicemail files were compressed and I could never get them to play properly. Sometimes you could hear some intelligent audio but it was drowned out in static. I tried many different variants of uLaw and aLaw. No datasheets on the codec could be found so I couldn't get the documented format.

 

Offline OrangeJacketGuy

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #10 on: May 24, 2014, 11:58:23 pm »
Could a disk dump of the hard disk be possibly made available? Might be interesting with the right tools...
 

Offline free_electron

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #11 on: May 26, 2014, 02:22:02 pm »
Hey Dave,

nice teardown once again. Please keep us posted about the outcome of hooking up that hard disk drive to a PC.
About the file system: I'd guess it is a Linux-style ext2, ext, or hpfs file system if Windows cannot deal with the partitions right away.
Thank you!

Regards,
Joe
No it's not. These machines predate linux. The drive layout is most likely an OS9 or CP/M . My bet is on OS9 or a variation as the central cpu is an 68301 . Motorola.

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Offline free_electron

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #12 on: May 26, 2014, 02:30:47 pm »
The MIke & TErry Lawnmowers chips are ubiquitous in telecoms industry. Whaddayamean , nobody's heard of em ?

Protel actually made telephone exchanges before they made autotrax ... Bet your top aussie dollar they had Mitel parts in em.

These guys mike and terry started making silicon in the dark ageslike mid 70's...

And no , it's not a joke. MITEL really stands for MIke and TErry Lawnmowers. Their very first product was a lawnmower...

That 68301 is a motorola cpu , also very commonly used in telecoms apps. There is a 68321 as well. Kinda likea 8086 and a 286. (Of course not i tel compatible, im talking numbering scheme here. To indicate it is an instruction compatible upgrade)

Those twinstack cards you pulled out looked like the had mask programmed dsp on them. You said rams but the ti logo gave it away. Ti never made memories in that package. Part number is 320c-so mething. My bet is mask programmed dsp to encode decode audio streams.
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Offline hikariuk

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #13 on: May 26, 2014, 06:33:11 pm »
That 68301 is a motorola cpu , also very commonly used in telecoms apps. There is a 68321 as well. Kinda likea 8086 and a 286. (Of course not i tel compatible, im talking numbering scheme here. To indicate it is an instruction compatible upgrade)

The Atari Falcon and Atari TT used the M68030 family too; there was going to be a M68040 based Falcon as well, but it got canned (made it prototype stage though).
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Offline Tothwolf

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #14 on: May 26, 2014, 08:56:29 pm »
@12:24 I'm glad to see the fasteners mentioned. Choosing the correct fasteners when you are designing gear is an art in and of itself. Those particular screws look to be a washer head type and have threads made specifically for forming threads in soft plastic. You'll often also see trilobular thread forming screws in these sort of applications too, even for forming machine threads in metals such as steel and aluminum.

Also, older telecom gear makes excellent eBay fodder, working or not (both PBX systems and multi-line phones). Don't let the age of the gear fool you either. There are tons of older systems still in use and people are always looking for parts to repair or expand existing installations.
 

Offline free_electron

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #15 on: May 27, 2014, 06:59:18 am »
That 68301 is a motorola cpu , also very commonly used in telecoms apps. There is a 68321 as well. Kinda likea 8086 and a 286. (Of course not i tel compatible, im talking numbering scheme here. To indicate it is an instruction compatible upgrade)

The Atari Falcon and Atari TT used the M68030 family too; there was going to be a M68040 based Falcon as well, but it got canned (made it prototype stage though).
No, not 68030. 68000 68010 68020 68030 are one family. 68300 is totally different beast. Not even compatible.
These were dedicated telecoms processors
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Offline westfw

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Re: EEVblog #619 - Dumpster Dive PABX Teardown
« Reply #16 on: May 30, 2014, 01:36:09 am »
Quote
No, not 68030. 68000 68010 68020 68030 are one family. 68300 is totally different beast. Not even compatible.
Hmm.  Motorola had a series of chips MC683xx chips that were sort-of microcontroller versions of the mc68000.  They had a 68000 core (later "CPU32", "CPU32+", still basically 68ks), a bunch of on-chip peripherals (UARTs, timers, DMA) and chip-select generators, but little to no memory.  Most well-known was probably the MC68302, which was *THE* "ISDN" processor because of it had a "Communications co-processor" with three channels capable of HDLC/etc that matched up with the 2B+D ISDN stuff almost exactly.  MC68332 had a "Time processing Unit", MC68331 was more trimmed-down and primitive (the cisco-500 "Terminal Server" used a 68331.)  MC68360 was the "QUICC" that added Ethernet capability. (ISDN home router-on-a-chip, almost.  Except it came out at about the same time as the PPC "PowerQUICC" that performed better.  IIRC.)
http://www.freescale.com/webapp/sps/site/taxonomy.jsp?nodeId=018rH3YTLC61650795

I can't find a 68301 in Freescale's portfolio, but an online search for the TMP68301 shows it as a 68k-based chip in the same family.

 


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