Fostex B16 D does not Record

[simeon]

fix record

remove the two Alan screws at the sides of the front display
on the right side youll see Q4 transistor this is track enable enable switching ..
ie it enables the common for all the track's enable record .... switches
signal 'bypass' routes to pin15 each R/P card set

its a 2sc1815 and they are easily switched also and very often fail

check at its collector center pin for zero ~+_ 0 volts with all track enable switches on the main unit out
when one or more switches latched if the transistor is faulty its collector will 'float' around +18v even though the base pin is at +5v {pin 20 remote port}
this transistor supplies switching to enable all the onboard track switches even monitor track
and provide the signals "BYPASS" to each R/P card

this signal when you lock on a track enable switch its routed to pin 15 of
each of the track RP units plugged into the channel cards slots on the base pcb
you can get too the top pcb and etc via the back top panel

check pin 15 on a given track youll see the legend on the board for 'bypass' if its 18volts
all the time could not be switched on or not
then that track is in bypass mode and will not record

this bypass pin 15 should be pulled down by the press lock enable track switch
and its common too all the switches is transistor Q4...
pulls all the switches common to ground so letting BYPASS fall too low
for each enabled track

you can also test the enable disable internal switches if you had plugged in the remote head......1
pin 20 on the connector at the back for remote so pin one is here looking at it :::::::::::::::::::: <

will show 5 v if this signal is low 0v then the internal switches on the front wont work
and is connected too Q4 base via a pull up resistor to 5v and a 10k to the base of Q4
so it will and should show 5v
if pin 20 isnt showing 5v without the remote head connected this is a different story
hi on pin 20 will equal low on the collector of Q4 and enable the tracks switches on the machine
by pass on the tracks will fall on press at each track enable switch 'bypass' input pin 15 on the R.P cards

this is the only thing 'signal group' that affects every track record
only two other signals can like the bias osc block
but easy to test and confirm


and record will work again hurray!!!!
give it a try

 

[simeon]

to fix track flashing and fixed enable

Hi Folks,
Now to get back to the not recording issue.
All Transports, Monitoring .. Funktion.
What does not work are the Track LEDs 1-16 and it does not Record.
Yes I did depress the track selector and it changed to monitoring the input as well.
Just did not record onto tape. Hmmmm
Any Help?

i think two things
the front panel display leds and channels switches reset and pitch

will have a common ground and some transistors to allow flashing leds

i think its bad connections not dry joints but worn from moving and using
as its old one side 2d boards that suffer mechanical fracture stress
again take out the two alan screws each side of the switches and
few screws holding the switch etc board flip it and solder it up as needed

check the transistors and as it wont record perhaps Q4 channel !{defo not any on remote en/dis} bypass common Q1 2 3 deal with the led flashing etc

each channel switch is two pole one used for BYPASS go low on select
to select channel enable pin 15 of the channel cards goes low on switch press

the other pole deals with the leds in groups of a common transistor Q 1 2 3
ill recon is the linking wires and broken connections
as the switches get well used
so eventually you guys get some decent answers
one guy in the thread went on a rant about cleaning a head
and went on and on about baking tapes terrible
you just need a sealed box and use some gel packs

DRY NOT FRY


you know the thing you get silica gel avoid tape shed should work like a humidor for cigars etc box
few of them dry big box all tapes and slowly cure...
leave them a month
you can add more bags or take out a batch of bags and dry them in the oven on low <65c for 1hr or 2 you can then reuse the gel bags

na its a duff transistor
i replace 100+ a year of it or similar

its finding it !! or them

such as an open circuit collector transistor dare i say less than dirt cheep 2sc1815 < 0.1p over 1000 pieces even now
get one or more ebay is cool for 5 for a euro of 1815's

i would also be warned anyone
the voltage select in this unit has three levels
its mounted too the rear transport panel access behind the control board let out two screws it folds down
back top panel remove

110v usa etc
220v east germany or etc perhaps look for AC supply region chart on ebay
250v uk etc

be sure its set too the correct region esp if you got it from uncle fred in east europe
be sure its set right
otherwise youll stress the transformer
for instance if its set too 220v and you run it in the uk
it wont blow up but it will stress all the regulation stages
and the non regulated 26v will run at 31v
so be sure of the blood
then the bypass if needed too make the heart of the machine tick with bias and on track

above all you must use lead tin solder not the new stuff
max 18 - 20w iron or you burn some thin tracks
so surgical mask plenty of air avoid the heavy metals


punch control socket issues
if pin 15 on a switched on track R/P card record 'bypass' disable is hi at 18v {see above posts}
then that track module will not switch to record from reproduction mode at ic level ....

however the bias etc is set {punch etc } WTRE ‘when track record enabled’ mode
so you need to enable a track before it can be punched in and out etc

so this can be ignored till you confirm when you enable a full track set is available for record as individuals
and groups and all leds blink then set enable on record
and it does record as expected

i expect read the owners manual and follow the test one track at a time

B4 you solder anything
use a 4 socket uk extension bar

i am in UK i connect the earth while i solder

so i plug the uk plug in upside down so only the earth pin

then its static safe
after all this fostex is full of barely buffered CMOS
and do it right...

observe ESD rules so connect an earth B4 any solders change ics earth yourself also too the chassis before you handle the chips

 

[sweetbeats]

Thanks for this valuable information, simeon, and welcome! This is an old thread, but your detailed information will surely help B16 owners who are searching for help with these issues.

Thanks!

 

[simeon]

this fault will be also caused by plugging in the remote head whilst the unit is powered up

so also the plug at the back is REMOTE head...
pin 20 remote/local switching for enable remote or machine switching of the 'bypass' low at pin 15 on the R/P channel selected
on the machine set a low on pin 20 pull it to ground 1k res will switch off the enable record switches on the front panel of the machine
however they are set as record

39 37 35 33 31 29 27 25 23 21 19 17 15 13 11 9 7 5 3 1 <<< top right control remote socket at rear
40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2


i can help with schematic and board snips but i cant help with the service guides
i looked for easy help but had to find the manual
then the fault with only my pal for help
he read the 'story' and i looked for the answer with a meter

thanks for the great welcome!!!
if i know/feel like i helped someone else
perhaps i can help someone else
!!!
just had seen the post in research and back tracked....


upgrades :

you can drill a 1mm hole beside the sockets and add an led connect too power
if the led is red dont plug it in
simple additions save the grief ...!!
ie DEAD or SIMPLE
if its red its dead if you plug into it

service manual is 'her' {still bitchin at me and my pal !!!} for 50 bucks
he payed and wont share ive used a copy but man its worth its salt...
so are the keepers...
very clean crisp and nice pdf

musicparts.com/products.asp?Company=Fostex
look up B16 service manual
im sick i didnt spot the like and download all years ago
but sometimes when you cant find help then your number 1 too do it..!!!