UGS adventures

Member
Joined 2006
Paid Member
A nice Flat UGS picture...thanks François !!!
...had trouble finding the onsemi 2N5641..hence the 10K resistance...will change it when i find the transistor....Farnell shows it but it's BS ...they don't have it.
 

Attachments

  • ugs_almost2.jpg
    ugs_almost2.jpg
    95.3 KB · Views: 1,127
Member
Joined 2006
Paid Member
Hi guys,

Well this weekend finally tested my UGS.....I'm half happy. ?!

1 - Right hand ....no sound but i hear the relays switching input and volume.

2- Left hand;... lovely music but....module aligns properly until i check absolute offset...there i cannot get better then 250mv offset !!! but i get music. RH module adjusts ok offsets are at 0V.

3 - volume control is erratic with display type 2, type 1 is ok. with type 2 it goes up and down in erratic steps, for now i will use type 1 to debug first 2 malfunctions.

Would apreciate sugestions.
 
Hi CeeVee,

1- can you check supply voltages first ? Have you plugged the UGS module in the right position ? (Sorry to start by asking trivial questions ;) )

2- can you explain further please? What do you call RH module ? Where/how is 250mV measured and where/how is 0V measured ?

3- If I remember, you are building two UGS All Inclusive, the slim one (CheffDeGaar's one) and the actuel one ?
 
Member
Joined 2006
Paid Member
Hi Maousse,

Yes i'm building 2 UGS...but second one, the Slim version is to be an aluminum work of art...will take longer, right now i am testing the " Miope" version with the HiFi 2000 box.

I checked the supply voltages, they are at 24V exactly as i adjusted them.

I checked and adjusted each UGS module as directed in François' paper, following kivabien's posting.

Left hand Board, looking at the Preamp from the front, checks out ok at every step but when i measure the absolute offset...........250mV is the best i can do.
Relative offset is ok ( 0 V ).

To measure the offsets i have the inputs tied to ground and measure between ground and Out +.


The right hand channel is ok , both offsets at 0 V. but there is a problem somewhere in the logic because i dont hear anything on this channel.

This is what i would like to debug first because the offset should be revealed by a closer look at each transistor in the UGS module.
 
CeeVee said:
Hi Maousse,

Yes i'm building 2 UGS...but second one, the Slim version is to be an aluminum work of art...will take longer, right now i am testing the " Miope" version with the HiFi 2000 box.

I checked the supply voltages, they are at 24V exactly as i adjusted them.

I checked and adjusted each UGS module as directed in François' paper, following kivabien's posting.

Left hand Board, looking at the Preamp from the front, checks out ok at every step but when i measure the absolute offset...........250mV is the best i can do.
Relative offset is ok ( 0 V ).

To measure the offsets i have the inputs tied to ground and measure between ground and Out +.


The right hand channel is ok , both offsets at 0 V. but there is a problem somewhere in the logic because i dont hear anything on this channel.

This is what i would like to debug first because the offset should be revealed by a closer look at each transistor in the UGS module.

Hi CeeVee,
if I understand you right you have 2 different problems:
1. Offset
2. Display/logic.

Offset issue is independant of Display issue I suppose.

To n. 1.
UGS module are not M-Board dependant so you can swap left-right module without problem. This way you can check if there is a Board Problem or module Problem.

Adjusting offset with probe at output (mean pre-output) is not so good. As there is the volume control inbetween.
Best is between Ground and first pin of 825R (at the beginning of the volume control/ first relay). Cause these Res is directly connected with output of UGS module...

You can also measure relative offset between upper and lower 825R also.

Manu
 
Have you tried swapping the UGS Modules ?
Offset is the same ?
Still nosound on the Right Channel ?

For the left UGS module (the one with absolute offset), you may have swapped the two 25turns RV, it has happened to some folks. Better check the resistors than check the transistors :p

For the right motherboard, the mute relay may be permanently on, can you measure the coil voltage with and without mute ?

BTW, still with my silly questions, how do you ground the inputs before setting the offset ?

PS : Ha ha, Manu first to shoot :clown:
 
Member
Joined 2006
Paid Member
Hi Manu,

I adjust offset at output of UGS module....not preamp output.

It is not easy for me to interchange UGS modules because i have connectors that make it impossible to change over....idea being that you cannot make the mistake of connecting them with wrong orientation.:xeye:
 
Member
Joined 2006
Paid Member
Hi Maousse,

I ground the inputs at the UGS module input connector to the ground at that connector.

I was in a bit of a rush yesterday but i will have another slow look today, that mute relay i will look at.

Logic being, that since display logic drives both MB in parallel, then if one works the other has to as well.

malfunction can only be in the cable to MB or MB itself.

I exclude the cable because if i disconect logic cable to the other ,working, channel i can hear relays comuting input selection and volume settings....and yes i have tried diferent inputs with same result.

That mute relay is a must to try....we will see.
 
CeeVee said:
Hi Maousse,

I ground the inputs at the UGS module input connector to the ground at that connector.

I was in a bit of a rush yesterday but i will have another slow look today, that mute relay i will look at.

Logic being, that since display logic drives both MB in parallel, then if one works the other has to as well.

malfunction can only be in the cable to MB or MB itself.
About the UGS module's connector :
I did the same, female connector on one end, male connector on the other end, but I kept the same order for the two modules.

Talking about the RV, sorry, the last CheffDeGaar's schematic is changed for both 50R, it's better ;)
So just forget that part of my words :p

So, with both inputs grounded, turning either pots do change offsets ? Just to be sure one of the pots are not jammed.

OK for the mute relay voltage. The µC command is amplified on each motherboard with the switching darlingtons, so one may be dead. Please, DONT measure directly the µC ouput, as it may kill it. By measuring the coil command voltage, we see at the end of the chain if there is a problem, then we will go upward the command signal, step by step.
 
Member
Joined 2006
Paid Member
Both pots in UGS module are now 50 R ?

...I have one 20R ( absolute offset ) and one 50R for relative offset.
even so...250mv is a BIG offset, the explanation has to be another one.

Yes i hear you ....don't touch the ATmega if you can, i will measure at the sharp end......at the relay.
 
CeeVee said:
Both pots in UGS module are now 50 R ?

...I have one 20R ( absolute offset ) and one 50R for relative offset.
Huh.... Sorry, just reading fast on the first post :clown:, and only the first design schematic has two 50R RV. So my remark still has sense.
Just be sure you didn't swapped the 50R and the 20R ;)

And looking for the problem, I ask you to check also all the resistors. One may be at the wrong place, so wrong value. Look around the 50R RV, aka Rs1 Rs2 Rs3 Rs4
UGS_V3a.gif


But first, I would like to know if the 50R has some action and is not jammed (it can happen). In that case, of course, you cannot adjust relative offset.
 
Hi CV
Sorry for delay, but I have to do real work sometimes...
Thanks to Maousse and Manu for being so quick and helpful in the meantime ;)

Concerning the "big" abs offset, what is the JFets grade of this module ? BL or V ?
If they're "V" grade, you should try to increase degeneration resistors to get down to 3.5mA bias current in the JFets.
 
Member
Joined 2006
Paid Member
Hi Cheff,

There is a great team here....ofcourse the band leader is always a pleasure to hear!

My Jfets are BL ....still have a dozen or so of each.
I'm inclined to a stupid mistake...like a wrong value resistor, will check.
my bias current if i remember correctly, i'm at work, is arround 3.2mA.

Thanks