Dynalo troubleshooting problems

[edwtsui]

Hi folks,

I am building KG's dynalo but encounter some problems during troubleshooting, would like to seek your help and advice.

Referring to the schematic and the construction guide below:

http://www.djgardner.com/headphone/gilmore/dynalo/layout/Rev-C/dynalo_rev_c.pdf

http://www.djgardner.com/headphone/... Detailed Construction (STACKOFHAY Edits).doc


1. In step 17.2, it said voltage across R11, R15, R41, R45 should each read about 1.0V. I am using LED with forward voltage of around 1.8V instead of 1.6V, so expected that the voltage across R11, R15, R41, R45 is more than 1.0V. I measured 1.16V across those resistors, is there any problem for not using the LED with 1.6V forward voltage?
2. The voltage across R19 and R49 should be each read about 0.8V, why?? How to calculate the voltage across those two resistors?
3. Voltage across R23, R24, R53, R54 should each read about 0.37V. Again, I don’t know how the 0.37V is calculated, can you show me how?
4. About the chassis wiring, I installed two RCA input jack and 3.5mm output jack on the chassis. I don’t have any problem on the input wiring as I can always twist a pair of wires on each RCA. However, for the 3.5mm output, there are only three wires (L/R/GND), how can I twist them together? Should I twist those three wires together? Or should I twist L/GND and R/GND and terminate both GND wires to 3.5mm GND terminal?

 

[edwtsui]

Can anyone help for this case?

 

[lineup]

You should adjust to get 2mA across R11 and R15.
If you use a higher voltage LED,
you must probably increase the value of R11/R15.
Like 560 Ohm or even 680 Ohm.

When the voltage across R11 divided with R11Ohm is 0.002
then you have 2mA.

 

[edwtsui]

You should adjust to get 2mA across R11 and R15.
If you use a higher voltage LED,
you must probably increase the value of R11/R15.
Like 560 Ohm or even 680 Ohm.

When the voltage across R11 divided with R11Ohm is 0.002
then you have 2mA.

Thanks. For Q1, I can replace the LED with forward voltage 1.6V. How about Q2-4?

 

[lineup]

I should add
that it is not at all critical to get EXACT 2mA.
1.9 - 2.1 will do.
My guess is you should use 600 Ohm for those resistor.
But 560 may be good enough.

 

[edwtsui]

If current flow through R15 is 2mA, then current flow through R1 & R2 is 1mA each. Voltage across then is 5V. Voltage across R17 would be 5V-0.6V=4.4V. Current flow through R17=4.4V/1kohm=4.4mA. Voltage across R19 would be 4.4mA * 215ohm = 0.946V. Seems there is a deviation between my calculation and the value from construction guide. Something wrong??

 

[lineup]

If you can get 1.9-2.1 mA through Q1 and Q2, then you should be pleased.
Your calculations are only calculations.
However 4.4 mA seems about right.

Now these are only numbers. The reality can be a little different.
Many transistors for example drops 1.65V or even close to 1.7V.