My Pearl One. Some questions

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
B

blackdod

Member
Joined 2011
Thanks NAR

nar said:
Make sure regulator works fine first.

I assume you know on Pearl PSU is not symmetrical, so pin negative and GND are the same ... it's ground reference, hence 0V.
Click to expand...

Yes, Ok When I check the Q3 I have always the same result, 29 volt :confused::confused:

nar said:
Check bipolars pinout and orientation.
For example, ZTX 450 and BC550C have their pins reversed, e.g. if you use BC550C instead of ZTX 450 you must mount them 180° reversed referenced to silkscreen transistor print ...

10 mV on R25 means intended current does not flow correctly. You should have about 50 mV ...

Hope this helps,

Best

nAr
Click to expand...

Today I have come ZTX450 :house:, so tomorrow I'll get to work again in the boards.

Let's see if I have luck!

Regards
 
B

blackdod

Member
Joined 2011
Hi

I have changed some ZTX450. I managed to improve voltages, but I'm having problems in Q4. :(

I removed a SK389 and.... I've seen in Q4 area I have 14 volts !!!!, so I'll replace SK389 by a pair of 2SK170 if this component is the source of the problem.

Any tips for mounting the 2SK170? :cool::cool:

Regards
 
B

blackdod

Member
Joined 2011
Hey guys

I changed the SK389 by a pair of 2SK170 and now I have better results in one of the boards.

In the left channel, I have a voltage of ,07 Volt before the R25. In Q5 area I'm still somewhat high voltages . In the area of ​​the Q8-11 I have voltages of .06 to .09 volt. Is this correct or do I have to change the 2sk170 in this area?

An externally hosted image should be here but it was not working when we last tested it.



On the right channel (yes it´s blue ) still have problems in the area of Q4, I check 29 volt whith a new pair of 2SK170. I changed the Q4 (ZTX450) but the result is the same.

An externally hosted image should be here but it was not working when we last tested it.



Anybody can give me some idea?

Regards
 
nar

nar

Member
Joined 2002
blackdod said:
Hey guys

I changed the SK389 by a pair of 2SK170 and now I have better results in one of the boards.

In the left channel, I have a voltage of ,07 Volt before the R25. In Q5 area I'm still somewhat high voltages . In the area of ​​the Q8-11 I have voltages of .06 to .09 volt. Is this correct or do I have to change the 2sk170 in this area?

An externally hosted image should be here but it was not working when we last tested it.



On the right channel (yes it´s blue ) still have problems in the area of Q4, I check 29 volt whith a new pair of 2SK170. I changed the Q4 (ZTX450) but the result is the same.

An externally hosted image should be here but it was not working when we last tested it.



Anybody can give me some idea?

Regards
Click to expand...

1st channel seems to be working about fine, even if some voltages differ

On the second one, some voltage readings are illogical, like after Q3, about Ok, but after, reading down shcematic the readings go up, which is impossible :eek: so, might need to change Q5 and the 4 jfets too; on the 2nd stage Q4 and the 389 seem blown ...

nAr
 
B

blackdod

Member
Joined 2011
Hi Guys!

Thanks for the replies.

I've been working on the blue channel and I changing:

Q4, Q3, Q5, 1N4739 and C15

Inexplicably, I had a short and this produced these values ​​so strange in that channel. :(

Now these are the new values:

canal%252520derecho.jpg


The voltage on Q8-Q11 is very similar between both channels.

Right now I'm thinking of changing again Q4, since the values ​​are still quite different from the scheme.

Can I use my second stereo?

Regards
 
nar

nar

Member
Joined 2002
blackdod said:
Hi Guys!

Thanks for the replies.

I've been working on the blue channel and I changing:

Q4, Q3, Q5, 1N4739 and C15

Inexplicably, I had a short and this produced these values ​​so strange in that channel. :(

Now these are the new values:

An externally hosted image should be here but it was not working when we last tested it.


The voltage on Q8-Q11 is very similar between both channels.

Right now I'm thinking of changing again Q4, since the values ​​are still quite different from the scheme.

Can I use my second stereo?

Regards
Click to expand...

17V seems too high on the drains of 1st stage jfets.

Seems there is still problem in the Q5 / Q4 area. The K389 seems alive but passes the double of the current it's designed for.


Try the other channel with the LP turntable ... can you hear music ?

Best,

nAr
 
B

blackdod

Member
Joined 2011
Hey guys!

Thanks again for the replies!

Right now I'm listening to an album of Chet Baker (... in NY) on my new Pearl! :):):):)

With voltages as they are, the two channels sound great . In a few days, I will change the channel Q4 law to lower the voltage of 20 volts and leave it exactly the other channel (13 volt) for safety, because I haven´t any ZXT450 on good condition (again).

I selected the input impedance of the switch that I mounted on the back you can get a good fit.

The only noise "suspect" is a constant HUMMMMMMMMM. I guess it must be due to a mass.

Any recommendations?

Best Regards
 
nar

nar

Member
Joined 2002
blackdod said:
Hey guys!

Thanks again for the replies!

Right now I'm listening to an album of Chet Baker (... in NY) on my new Pearl! :):):):)

With voltages as they are, the two channels sound great . In a few days, I will change the channel Q4 law to lower the voltage of 20 volts and leave it exactly the other channel (13 volt) for safety, because I haven´t any ZXT450 on good condition (again).

I selected the input impedance of the switch that I mounted on the back you can get a good fit.

The only noise "suspect" is a constant HUMMMMMMMMM. I guess it must be due to a mass.

Any recommendations?

Best Regards
Click to expand...

The turntable GND must be connected to Audio GND at phono preamp.

For internal wiring, do a star ground from PSU GND node. Each place you need a GND reference, use a single wire from PSU GND to make it. Only inputs can be connected "as is", eg the normal way. A shielded cable in that position may help.

Best,

nAr
 
nar

nar

Member
Joined 2002
blackdod said:
Hey guys!

Nar, I followed your advice and the noise of mass has disappeared.

I can only regulate the right channel Q4.

In my input impedance selector I used the following range:

10 Ohm

40 Ohm

100 Ohm

250 Ohm

500 Ohm

1K Ohm

47K Ohm (This is the resistance R27)

Regards
Click to expand...


Good, but you may want to investigate more to see why one channel reg. works, and the other doesn't.

If you post again some new voltages, maybe we could help more

Best,

nAr
 
B

blackdod

Member
Joined 2011
Hey guys

I measured the voltage (outputs GND carrying to PSU) and I have had virtually no changes. Voltage on Q5, 17 volt

Right now I have connected the GND output to the Rcore-ground and although the voltages are equal, but the HUM has completely disappeared.

An externally hosted image should be here but it was not working when we last tested it.


On this picture you can see the output GND connect to PSU GND.

There is still detail that is escaping me. Still, the pre sounds pretty good.

Does the 9 volt battery will have something to do?

Regards
 
Johnloudb

Johnloudb

Member
Joined 2008
What is the voltage at the base of Q5. It should be 1/2 voltage of that at the emitter of Q3 (~24v), so close to 12v. If it's not then it could be that your resistors are not both 10k ohm, or there is a solder joint that is not solid, or maybe damage to the transistor Q5.

Those are the things I would check for. You can measure the resistance of R18 and R21 to ensure they are both 10k. The circuit shouldn't affect the measured value much at all, with the circuit turned off, of course.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom