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Hi I have a beomaster 1900-2 that wont power on after I recapped it, replaced the rectifier and replaced the emitter resistors as 2 had gotten far too hot
My first issue I have no idea what wire is live the black or blue?
Then after that where should I look?
I have a meter but not overly sure how to use it for testing components really any help really really appreciated.
I posted some photos of the Beomaster 1900 power switch and 15 VDC supply here recently.
-sonavor
Many thanks
I'm confused though as you have a brown wire 3.3Mohm to ground? I'm sure I don't have that
And judging by your labeling it doesn't matter what polarity the incoming power is?
I think my 2a fuse is blown as it's failing continuity. I'm sure if originally put the rectifier in the wrong way around (I'm new to electronic tinkering)
The incoming line voltage is AC so the polarity doesn't matter.
Ok so I keep blowing the 2A fuse that's why it's not powering on
Where is best to start looking?
What was the condition prior to working one it? Did it power on before the recap?It sounds like you have a short somewhere. You plug the Beomaster 1900 in, turn on the main power switch which should start up the +15VDC supply. The 2A fuse for that path blows so something is asking for way too much power...especially when the power supply is only starting up in standby.
If it powered on okay prior to the recap then you can narrow your search to things you touched during the recap.If not, then it is a little more difficult.When the power switch is turned on only the +15 VDC power supply should run. The relay that turns on +-31 VDC to the output amplifier should be off.With the Beomaster 1900 disconnected start going through the +15 VDC power supply components looking for a short. In these cases it really helps to have a variac with an ammeter to slowly apply AC to the Beomaster. If the current starts getting too high as AC voltage is dialed up you know the problem still exists. That helps prevent a long trial and error period of blowing 2A fuses. Adding a dim bulb tester to the mix can also help checking for power supply shorts.
It can also be helpful to post detailed photos of the areas you worked on. Someone here on the forum with sharp eyes might spot something you are missing.
Well progress 2200uf cap was wrong way around it turned on great start putting it back together then turn it back on then boom one of the new 5600uf caps turns it's self inside out :(
Those 5600uF power filter capacitors have to be wired opposite polarities to each other.I show a good picture of those on this blog post.
Yeah now I look at my picture taking apart pic I realise where I went wrong ;)
Right put the original caps back in
Now when I take it out of standby the 1.6A fuses pop not both at the same time
When the Beomaster 1900 goes from Standby to actual On it engages the big relay which allows the +-31 VDC rail voltages. The two 5600uF filter capacitors you had to revert to try to charge up. The 1.6A fuses are for each of the Beomaster 1900 transformer primaries. When they blow it is an indication that the Beomaster is demanding too much current. It doesn't provide any finer grained information that that. You will have to do more inspection to look for problems with the recapping. Another thing you might have to do is to desolder power relay control wire so it can't engage. That will prevent the +-31 VDC rails from trying to come up. If the Beomaster 1900 can come on without the rail voltages then you will at least know that the problem is in the output amplifier section somewhere. You have to be extremely careful doing that though. Loose wires must be completely insulated against accidents. Don't leave any loose, bare wires exposed.
thanks for all the info.
it took it out of the case again to check nothing was touching etc now im getting the 2A fuse blowing again
its not letting me upload images for some reason
It is time consuming but you have to isolate what area has the problem.I would probably regroup and start again from the AC/main power switch to make sure the power and ground wires are all perfect up to the point that they attach to the main board. Once that is verified you can start start checking the main board. For these checks you can disconnect the tone control and FM tuning board to give you more room to check things.
On the trace side of the board study the solder connections and make sure you don't have any splashes that are connecting pads that should not be connected.
How much of the main board did you disconnect when you changed out the capacitors?
All I disconnected was volume light board, station light board, tone control board, lights for tone control and power switch oh and the 2/4 Chanel switch
Replaced filter caps, beoparts cap kit, rectifier, emitter resistors
C71 not sure if it's the right polarity
C71 should be oriented with the negative polarity lead to the ground solder pad.I didn't see your answer if you gave it about the condition of this Beomaster 1900 before you started working on it. Was is functional where you could turn it on?
I have always found it difficult to replace components on the main board of the Beomaster 1900/2400 receivers unless I partially removed them. There just isn't enough room in back row where the power transistors connect to get the capacitors in that area of the board out (and new ones in). I am wondering is some leads on components in that area got bent where they are touching.
Sorry yes all inputs worked all tone control worked only issue was right channel was much quieter than left
I had it totally out of the case I just didn't disconnect the transformer or anything . I did find some resistors that were touching so I straightened them up but possibly when I put it back in some bent again
Okay, then the problem had to have been introduced by the recap work. Either the actual work or due to the board being removed and reinstalled.
Initially your problem (after the recap) was that the 2A fuse for the +15 VDC blew. That prevented the Beomaster 1900 from even going into Standby mode.That turned out to be due to the +15VDC power supply capacitor (2200uF) was installed with reverse polarity. You corrected that and the 2A fuse was then okay and the Beomaster powered on to Standby mode.When you tried to turn the Beomaster on (out of Standby) your -31VDC power supply rail filter capacitor blew out because it was installed with reverse polarity.You had to reinstall the original filter capacitors for the +-31VDC rails in order to continue but with those installed you started to blow the two 1.6A fuses to the transformer primaries when you tried coming out of Standby mode.Now you are back to the starting problem where you cannot turn the Beomaster on to Standby mode without the 2A fuse blowing again.That is extremely difficult to diagnose remotely.You have to go back to square one I would say. The first thing is to be able to get Standby mode back.I think I would start with checking the main transformer out. Verify that the primaries and secondaries are good.I would also test the two bridge rectifiers. The one for +15VDC and the large one on the frame for 31VDC.Both the transformer and bridge rectifier checks would be with those components removed from the Beomaster 1900 circuits.I would probably remove the two 5600uF filter capacitors for the +-31VDC rails and cover the wires that go to them with insulation so they can accidentally touch anything. Then concentrate on getting the +15VDC back working. That means the Standby mode and the On mode (except without rail power). The Beomaster 1900 does get a -12VDC power voltage for the volume control circuit that is derived from the -31VDC rail voltage. So that wouldn't be functional. But I believe you should be able to check if there are any issues with circuits that run off +15VDC.Once you are back to that point you can tackle getting the +-31VDC power connected up. That includes getting some new 5600uF filter capacitors.I can't say for sure whether the incident with the -31VDC capacitor could have caused any damage to other components in the Beomaster 1900.I suppose that is a possibility as well.Not an easy road by any means but with effort it is solvable.-sonavor
Cheers for all your help with this I'm just waiting on more fuses arriving today
It's the first time I've ever done anything like this so I'm finding it a challenge as I'm not exactly sure what everything means
I'm loving your blog though!
I don't think I can afford to by a variable transformer and scope yet though. This has already cost me most probably 3x the cost of the now broken 1900-2
Duplicate
Challenges can be fun. Especially when the final results are good.
Try to plan out your trouble-shooting where you don't have to blow any more fuses though. You need to have spares of course but they should rarely blow.-sonavor
15v rectifier
m + > - R
m- > ac R
.5v drop
m- > + R
m+ > ac R
big rectifier
what way should c91 be facing ? as on the board the white semi circle (shouldnt that be negative) was on the positive so facing down the board like in the pic here so whats right the pic or the silk screening on the board? mines a 2903 too btw
at 9 i get 16.87v
at 10 i get 0.1
at 6 i get 23.3
at 8 i get 23.33
where else do i need to measure?
so i take it that means its bust as im only getting power at 9 not 10
I am not sure what you mean by 23.2V at 6a.16.87 VRM going into the bridge rectifier should result in around 23 VDC coming out of the bridge rectifier. So that part looks good.So your Beomaster 1900 is able to start in Standby mode with the 2A fuse in place?
i was going off the numbers on the pcb's
nope its still popping fuses
the the emitter resistors i used are 0.47ohm 5w is that an issue as orginals are 2w i think
blue 6 &8 on the schematic green pin 9 getting voltage red line is pin 10
Okay, that makes sense now. You were reporting the AC voltages of the transformer secondaries.Your values of 16 and 23 sound good then.So right now, you are back to where you can't get to Standby mode on the Beomaster because the 2A fuse will blow if it is there.That means you can't try going from Standby mode to actual On mode (because you never get +15VDC).The wattage of your emitter resistors is not a factor. The only problem there is if you shorted something when your replaced them.Something has to be shorting out your power supplies for it to be blowing fuses.
right all but 1 transistor is toast
I see...the output amplifier transistors and a transistor in the +15 VDC power supply.TIP 141 and TIP 146 Darlington transistors.
TIP 31A PNP transistor for the +15 VDC power supply.
I guess they didn't like that -31 VDC rail voltage incident.
You should be able to find replacements for all of those.
It's not the first time the right Channel has had them replaced its tracks are buggered on both 300 and 301
great news after taking out tr201, tr301, tr 300 and tr27 standby light comes on !
Okay but don't continue until you replace TR27. The +15VDC power supply needs that.
I am going to guess that the -31VDC filter capacitor incident was the root cause for the TR200-TR301 Darlington failures.There could be other problems so check out the other components that connect to the +-31VDC rails.
One other thing...When you replace the power transistors do not try to turn the Beomaster 1900 on without mounting those transistors to their heatsinks (with proper thermal insulators). -sonavor
wont normal cpu thermal paste be ok ?
ive ordered upgraded darlingtons 142 and 147 as they were easier to get hold of and a bunch of tip32c mine had a 32A fitted but i couldnt get that easily
and a new pair of 5600 caps
I think a lot of the cpu thermal paste is conductive.On the transistors that press against a heatsink with a spring such as the Beomaster 1900/2400 I have been using Sil-Pad product for the thermal conductivity. When I don't use the Sil-Pad production I use Wakefield 120 white thermal paste.
ok ordered some of those too
Just put in a new tr27 and I still have standby only krps it on for a few seconds as it wasn't heatsinked
hi anyone any idea what gauge wire i should be using for replacing the black wiring in the unit just need to extend/replace 1 or 2 bits also what gauge wire is used on the switch as they could do to be made a bit longer too
Are you referring to the speaker terminal wiring?
hi its back on and stays on in standby but as soon as i take it out of stand by it goes straight back to standby
yes i was
as for the switch ones i just cutup a power cable :)