Rowe Saturn Jukebox Amplifier problems

[amandandme197]

You mean the 4 output transistors or the speaker output plugs?

[ed12]

until this test is over with the 4 output transistors

on my pervouis post i made a mistake
for u..we will be switching the ground with the vcc when we do the - voltage chk
so at that point the red probe will go to ground and the red probe will measure
the minus=- voltage
this is because we are using an analog meter
my bawd sorry..
now with everything back in expect the output transistors
go ahead and place your 2 lights into the fuse holders >just tack them there<
u should find +40 volts dc on both sides of 1 light
and - 40volts dc on both sides of the other
if so...2 of your leds should be off >overload<,if so we order transistors and fuses
mica's and grease
this applys to 1 driver channel olny..as u olny have 2 lights
but just remove them out
and place them in the other driver board
and repeat step 1 and 2

and as a saftey measure here
give the main caps about 30 mins to drain down there charge..reason is there is no real load for them to work into
 the driver board will pull it off abit slow but it will do it

ed

[amandandme197]

Ok ed, call me stupid, but without the 4 output transistors, how would we know if they are bad?

[ed12]

as has been explained...
and stupied is not in this..
the outputs a darlington with internal resisters
it is all but impossable to chk them right with out a proper piece of test eq..
200.00+ dollars
the olny real test u can do is >chk for shorted transistor<
on the leakge test they will show bad on any meter
analog and or digital
u need a b-x-k transistor or a small pico job to do it proper
and it is just not worth the money to buy them as a 1 off unit..
it is cheaper to do it the way u are
and then order in the new stuff u need
u see the leakge test is a mind tester even for seasoned repair techs
without another knowen good 1 to ref to
it is a guess at best
if u had a shop like mine where i stock them it is a cake walk
but for u this is not the case

ed

[amandandme197]

No, I do remember yo telling me about that, I guess what I am trying to say is that if those 4 transistors are removed, how can we do any kind of testing? So I should unscrew all 4 transistors, and remove them before we do this light test, hook everything up as it was before the amp went bad, and turn the juke on, then do the voltage test?

[ed12]

yes yes yes remove them.....
now do not turn this amp on with them in place........
a nice thing to do here and we all do it
is mark them 1.2.3.4 and the hear sink the same way 1.2.3.4
this way u know where the new ones go....
DO NOT PLACE IN THE NEW 1'S UNTIL WE ARE
A DONE TESTING
B I GIVE U THE LOCATION ID
u see they are npn/ pnp matched pairs
as a rule they will come packaged toghter
ie 2 transistors in 1 pack..
ie npn/pnp for 1 channel
we do not mix them up..at all costs

ed

[amandandme197]

Got ya buddy.

[amandandme197]

Now the ones that are in there now are the ones i put in there. Do you think i screwed anything up when i turned it on then, and should i still number them since they may be wrong when i put them in?

[ed12]

please do as i requested
u are in the home run right now :3rd: base
lets not play games with it now
u have to under stand short of a dead short there is no way u can test them
a=u do not have a pair to compare to
b=u are using an analog meter
even i do not second guess myself in these matters
and i no longer have any idea as to how many amps i have done
there is a set prodocol here..we all follow it
it costs less $$$ and saves a boat load of time

ed

[amandandme197]

I will and i trust believe you. I was just trying to say I have the ones that I removed still (that were in it when i bought the juke), and I have the ones i put in after the amp stopped working a couple weeks ago, and that did not work as soon as I reconnected the amp. So i have 8 total is what i was trying to let you know, and that the replacements that i put in before i contacted you guys, that did not work. I will do as you say buddy, but just wanted to let you know that I had the originals still, and the replacements, all which do not work.

[ed12]

i understood u
from the start
u may have been shipped un-matched pairs
all to common when u buy the of fle-bay or even mouser/digikey
u must spec matched pairs..as i explained they the npn/pnp's will come toghter
in 1 pkg so u will get 2 pkgs of npn/pnp and the other will be the same
npn/pnp,they will be marked  >mp's<,this is the way u want them..
the reason i do not use the old 1's
a= the mains fuses blew..40v at 8amps =320 watts..? on a 250 watt amp max
that my friend is a dead short
same reason we will replace the micas..
mow on to the old and new
u can with the analog meter
rx1 or rx10
chk c-e c-b  bet u find a short there
but it is of no nomer..if the pairs were not matched to start with
the self biasing diodes would have snapped them...
u have to under stand the full theroy of your amp
it is a push pull amp..the outputs
with a qusi drive..the qusi drive makes it diferrangle
which in easy terms means the driver is just about always in a on state
and it is a postive feed back style amp..even more of a problem child...
just be glad u are not dealing with a mosfet amp..yours is linear
will not any near digital..thk the lord

back to the old 1's transistors
ever had a cd u loved skip..and used it as a frishbe ?..
use them as a lesson learned..move on

ed

[amandandme197]

I got ya now. No they were not sent as matched pairs. I ordered them all sepperate. I thought as long as they were pnp and npn, they were good. I see now what you are saying.  Ok, i will do all of what you said ed. Sorry if I got on your last nerve, i just didnot understand that they are supposed to be bought as a mp in the same packaging, thus making me wonder what was wrong. Ok, i will do as you said and get back to you. Sorry

[ed12]

never never say sorry to me
if u did not understand the rules
how would know how to play the game...??
and on my last nerve? i think not..this is a pleasure for me..trust me
my new gig with the rasberry pi will come as i want
i am just working out a few kinks in my head..
plus they put me on another med..which i did not want..
reason is simple..cannot ride my honda..and that 1 gets on my nerve
your amp is  :a: a pleasure to help u with,:b: i get to refresh crap i already know
no foul...

ed

[amandandme197]

Lmao, thank you buddy. Sorry about the ew med. I feel your pain

[amandandme197]

I just didn't want you thinking i was one of those "you can't fix stupid" types of people........lol

[lilshawn]

basically what's going to happen is: the transistors are a valve. if there is an issue with the preamp board it will drive the output transistors full on instead of leaving them closed until it's time to play something and drive the speaker coil.

if we measure the drive going out to that transistor and find anything odd, we know something is up and needs to be investigated further... if all seems good, we can plop them back in and HOPEFULLY be good to go again.

[amandandme197]

I got ya shawn. I have all boards back in, connected, transistors removed, and bulbs in place of fuses. Now i guess i will plug the amp in the amp outlet. I assume i need to connect all the speaker hookups to the amp? I will wait to hear from you before i go further.

[lilshawn]

no, we are just going to check the predrive. we won't need speakers for that. you can just have the amp sitting out on the bench for that test.

the lightbulbs are going to give you a visual indication indication of how many amps are passing through the driver board

[amandandme197]

Awesome! I hate lugging it in and out of the juke.

[amandandme197]

Both d6 led lights are lit. I unplugged it to be safe.

[ed12]

ok
so far so good
i will chime in ltr and help finish it up now
then we can order our new stuff
and u will have a working amp again

ed

[amandandme197]

 Also, no overload lights came on, so  I assume that is good as well........ 

[ed12]

ok
1 driver board at a time
place in the lights where the fuses were
turn amp on
of course U HAVE REMOVED THE OUTPUT TRANSISTORS
and see if the light come on dim/med/bright
if dim
turn amp off and wait about 30 mins for the caps to discharge
place lights in other driver board and repeat

at any time if the light comes on bright shut it right off
dim to no light at all  is all i will accept at this point
do that first then get back to with your results

ed

[amandandme197]

Ok, on the first board that had the blown fuses, the lights did not come on at all.

[ed12]

perfect
now do the other board
if it passes the musterd test
we order  matched pairs
micas/silcon grease
and fuses

ed

[amandandme197]

Sounds good buddy

[amandandme197]

Unsoldering from the first board now.

[ed12]

u are so colse to the home run i can just about see shawn on base..
just REMBER U ARE NOT USING THE OLD OUTPUTS..
or all is for not

ed

[amandandme197]

All clear. No lights.  Nope, all 4 of the recent outputs and the 4 original ourputs are put away. Just kept out the screws grease and 4 new insulators

[ed12]

order away
if u want i will chk my main line for matched pairs ?
as i trust them

ed

[amandandme197]

That would be great. As long as they are cheap enough, I will do that if you find anything. I will order some 8a fast blow fuses from ebay. So did the lights confirm everything seems to be good?

[ed12]

ok i will ask my suppiler in the am

yes they said the driver seem to work right

now before we drop in the new finals
we will with the new fuses in do a test on the final driver circuit
it is easy...we will olny be looking at  drive voltage to the base of the finals
to make sure they are not beening turned full on..this is where back about 4 pages ago i asked u if u had a audio source..u said no so i went this way..
same out come just a dif way of doing it

now the lights will be used instead of your speakers,for our final test
before we tie it back into the juke

side note here..i will be doing deep scan on this my main box tonight
it takes 14.30hrs to scan 6tb of drives
and yes i said terra bytes,so do not expect me before 6:pm est
i will be around tonight for another byte or 2..

[amandandme197]

Awesome buddy. That is no problem. No need to explain yourself, as I appreciate your help any time you are able. It means a lot. If it were not for you, and shawn pitching in when your gone, I would be lost. I am just greatful for any help.

[ed12]

my best price tonight
without my usual chit chat with the person in charge
is about 4.55 each..about 9.00 per matched pair
not to shabbey for on line..
but i will make the nessarey >hey dude< kinda calls tommrow

they are for the record
2n6284 and 2n6287
a swift nte crosses them to mp's
but i do not buy nte..........
my manual even places them right..
if u need i can get a scan for u..so we do not fault now ?
now mouser lists them seperate..this is bad for our app
i did not chk digikey yet but i will

ed

[amandandme197]

Awesome, awesome, awesome!!! That price sounds good to me Ed. I think that is pretty close to what mine were each when I bought them from  Allied Electronics, but they were not mp. Would I be able to pay you through paypal, or pay them through paypal (which ever one of you would be sending them)? The scan would be helpful if it is not a problem. I thank you buddy. Oh and they are the numbers you posted.

[ed12]

no u guys can do it
i willl just clear the lanes as it said....
and yes i will go get a pdf for it

ed

[amandandme197]

Thank you so much ed!! 

[ed12]

well
that took a little longer then i thought
27hrs
found 2 tracking
1 cookie
1 worm

after what i was told today
we can ditch the idea of >mp<..why i am out on as of yet..
but do not do any thing..i will dig in tighter
reason is i just want this amp up and running

ed

[ed12]

ok i have tracked down a pair

now short of ami-man having >mp's< ?

digikey
mouser

it seems the mp's went :eol: >end of life<
if u want i will nose around jukebox list or phono land
allen is a @ at phono land,and seems like he may come to the cause ?
i know i olny have 1 pair left..which i want for testing reasons
 that said,i will poke through my nte stock etc,if i have them your welcome to them
just please do not buy them from flea-bay...

nte 251 =2n6284 hfe=2400
nte 252 =2n6287 hfe=2400
thats what mkes them a matched pair  >hfe<

ed

[amandandme197]

Thanks ed, I appreciate it. Do you think I should get extras if they are that hard to find?