My_Ref Fremen Edition - Build thread and tutorial

[voxxonline]

Identical

 

[fromthecrowd]

Wiring the transformer

Unlike an example with Antek toroid, my toroids have secondaries marked as in the given picture. No problem with continuity. But how to find out which end goes to AC and which to NAC? Advice is needed, please!

 

[ClaveFremen]

But how to find out which end goes to AC and which to NAC? Advice is needed, please!

Don't worry it will work in either way, it's AC and each secondary have his diode bridge.

Let's say yellow AC1, NAC1 and white AC2, NAC2.

 

[voxxonline]

Dario, any ideas what to do or what to check ?

 

[ClaveFremen]

Dario, any ideas what to do or what to check ?

Start from basics, disconnect transformers and check that secondaries outputs 24V (in reality you shoud measure around 26V)

 

[voxxonline]

28 AC

 

[No 4]

Voxx, your actual mains voltage will effect the output of your transformers. My traffos are 22V @115v iirc. My actual mains voltage is almost always 125V (the other night it was 127V!) My secondaries actually put out more than 22V because of this.

 

[voxxonline]

So it means transformers are ok, problem is somewhere else
14.6 V values ok
1.25 V is ok
Output stood at 3 mV

Only discrepancy in 35 V value

Am I measuring it wrong ?

 

[fromthecrowd]

Don't worry it will work in either way, it's AC and each secondary have his diode bridge.

Let's say yellow AC1, NAC1 and white AC2, NAC2.

Thanks a lot! This being an audiophile amp with oriented resistors, I suspected nuances could be present

Only discrepancy in 35 V value

Am I measuring it wrong ?

Are you measuring AC or DC? 23,5 looks too much like 35 V DC measured in AC mode. Just in case.

 

[voxxonline]

DC.. suddenly relay started to click in and out ...

i hope i did not short ic201 while testing

 

[Marra]

Voxx can you measure across both of the 10'000uf caps; unless of course that's how you are already doing it.

 

[voxxonline]

it was 35 V

 

[ClaveFremen]

it was 35 V

Seems fine, why "was"?

 

[voxxonline]

Because I think I just shorted lm317 after tester slipped across contacts
clearly not my day today

 

[voxxonline]

So 35 on 10000uf caps , then what can be wrong ?


Panic mode off. Board is ok...

 

[ClaveFremen]

So 35 on 10000uf caps , then what can be wrong ?

Fine so main PS is OK, then measure voltage on C102/C202 pads, it should be +14.6V and -14.6V

Relay stopped chatting?

 

[voxxonline]

Yes, it is 14.6 ..just a bit off that value.

I powered off that board for now. I LM317 might be overheating now, it was very hot then I touched it.

 

[ClaveFremen]

Yes, it is 14.6 ..just a bit off that value.

I powered off that board for now. I LM317 might be overheating now, it was very hot then I touched it.

So both values are around 14.6 plus and minus, LM317s are hot, is normal.

DC offset, how it measure? Relay clicks normally?

 

[voxxonline]

Pardon, but what is dc offset ?
Relay clicked on and off few times, lm317 was so hot I almost burned my finger.

 

[ClaveFremen]

Pardon, but what is dc offset ?

It is DC voltage you measure on amp's output.

It should be as low as possible, less than 7-8 mV is optimal.

Relay clicked on and off few times, lm317 was so hot I almost burned my finger.

So you have relay chatter... so assuming that other transistors (BC546) are still good you could have DC on output.

To measure DC offset bypassing DC protection circuitry you can measure it on OUT (red probe) and PGND (black probe).

If you'll measure high DC offset probably the LM318 is gone and you'll have to replace it, otherwise the amp is fine and you should replace ALL DC protection transistors.