Christi's Ta3020 V3c difettosa

Ok Cristi, I didn't know about time delay, you were supposed by me to be in Europe and working for connexelectronic help desk

This is my fault, sorry

I want to tell you that I am really satisfied with the quality of the PCB, but unfortunately there is this problem

It's not due to my modifications because as you know R74 is on the other side of PCB respect to the R59 and R60 I removed, and well protected under the heat dissipator

I was thinking to bypass the R56 with an axial resistor soldered between C33 and INV2 pin

I checked the continuity between INV2 and ground and I read 90K ohm, same for the INV1 so it should work

But probably the biggest issue is to change gain, I'm scared about replace other smd resistor

i never said that i am in Europe, this can be seen from my address too, i am from Europe but living in China. and i am working at the helpdesk when i am not at job, designing something, purchasing parts, assembly, test, packing, shipping them, or whatever else i can do. anyway, as i told you before, if the board is not working, you can send me back at anytime and i can fix or replace for you, or refund the cost if you are not satisfied with. i think that this is fair enough. if you choose to repair by yourself, i can tell you that is not impossible to resolder this resistor size. i curently work with 0603, 0805 and 1206 parts without any problem and even with 0402 and 0201 sometimes. if i can solder 0402 and 0201 i see no reason why someone else cannot solder 0805 size. but please don't damage something else.
R74 is a bridge for BTL mode, and need to solder just when you want to use the amp in BTL mode.

did you really had to open 2 threads with this impressive name ?

Cristi, probably we have a case of misunderstanding

I opened the first topic just to get help to connect the PCB without damage something, and to not abuse of your availability; meanwhile I've continued to send you mail but without expecting an immediate reply

Then, when I discovered the problem with R56 I opened the second post, always to get some help to repair the PCB

I wish to avoid to resend you the PCB

Cristi ha scritto:
R74 is a bridge for BTL mode, and need to solder just when you want to use the amp in BTL mode.

so I didn't scrapped anything by mistake, R74 was never been there

Sì, la V3c ha il relay sulle casse, ma si vede che ha qualche problema. Io sulla V3b ho la schedina di protezione diffusori e NON ho il problema di bump e nemmeno il fsssh in spegnimento. Sulla V3c ci sono entrambi (almeno mia scheda)

Anch'io come dicevo ho risolto mettendo una scheda di protezione che non solo elimina i rumori all'accensione e allo spegnimento ma protegge anche le casse in caso di guasto ai mosfet o problemi vari che possano causare il riversarsi della continua sulle casse.. In questo modo il primo bump (dovuto ai condensatori di ingresso che si caricano) non può farlo perchè le casse sono fisicamente scollegate per diversi secondi dopo l'accensione, quello "shhh" che fa quando stacchi lo fa solo sopo pochi secondi quando la tensione di alimentazione tende a scendere e quindi nemmeno questo può avvenire perchè appena stacco la 220V automaticamente la schedina stacca subito le casse..
La V3C è l'unica scheda 3020 di Cristi che mi manca parte.. ma presumo che la parte aggiuntiva sulla V3C dovrebbe fare esattamente così.. quindi in teoria penso ci sia qualcosa che non va..

hawui1 ha scritto:
La V3C è l'unica scheda 3020 di Cristi che mi manca parte.. ma presumo che la parte aggiuntiva sulla V3C dovrebbe fare esattamente così.. quindi in teoria penso ci sia qualcosa che non va..

già, è quello che pensavo anche io, solo che mo chi lo dice a Cristi, se l'è già presa male perchè ho pubblicato questo topic

non so se avete notato il tono delle sue risposte, ho la sensazione che sia stato frainteso il significato di qualche affermazione da me fatta in questo topic ....

I designed the TA3020v3c to be used mainly with mains transformer. in case of using the board with SMPS, the diode D17 must be replaced with a 39V zenner diode, this because the DC voltage will be present on the supply rails after turn-off and will decrease in few seconds. when the voltage will go below the startup treshold of 32-35V the amplifier will decrease the sw. freq. down to audible freq and this is the zooming noise wich you might hear when power off. do prevent this to happen, the diode must be replaced with a zenner diode with higher voltage than that threshold. i tried 39V and is working fine. also, must be polarized opposite, with K to vcc and A to R69. this will not happen with a mains transformer because the voltage detect will dissapear when power off the transformer.
now, the bump. this is created when a DC component pass to the speakers. the speaker protection can prevent this if the timing is set corectly. (C47, R67) but if the input capacitors are larger than the ones which i put or the DC offset of the signal source is higher than 2-3V, charging the input capacitor will create the output offset. (remember that i said to not use larger cap than 10uF) to increase the delay before power on, just increase the value of C47 up to 47uF.

Ok Cristi, everything is clear now, thank you for the detailed explanation

My coupling cap are 2.7 uF, so well below the limit, anyway I'll try modification you suggested on c47, but ... ehm

I can't find any C47 on the PCB nor in the diagram for V3b

I designed the TA3020v3c to be used mainly with mains transformer. in case of using the board with SMPS, the diode D17 must be replaced with a 39V zenner diode, this because the DC voltage will be present on the supply rails after turn-off and will decrease in few seconds. when the voltage will go below the startup treshold of 32-35V

ok, so, installing this diode, I assume that the relay will go off when the supply voltage (per rail) will go immediately below 39V avoiding the "hiss zone" near 35V.. Instead with the transformer you could relay on a kind of AC detect circuit and therefore the relay was immediately opened upon AC being removed.. correct?

My coupling cap are 2.7 uF

If I understand correctly in this case there shouldn't be any bump, because the actual value of C47/R67 should cause a delay that gives the input capacitors time to fully charge before the speakers are connected, so in theory the cause should be searched somewhere else, superrobin could it be you did modifications to the input circuit of the board? And if yes could you please try to explain what you did ? This way perhaps somebody could be able to provide you recovery advices..

Ok, found it !!!

I removed the cap beside the R67, the label was under the cap

sorry

hawui1 ha scritto:
If I understand correctly in this case there shouldn't be any bump, because the actual value of C47/R67 should cause a delay that gives the input capacitors time to fully charge before the speakers are connected, so in theory the cause should be searched somewhere else, superrobin could it be you did modifications to the input circuit of the board? And if yes could you please try to explain what you did ? This way perhaps somebody could be able to provide you recovery advices..

Ok, I list all the modifications made to the PCB, and apologize in advance if we discover all the trouble has been caused by me

1) removed R59 and R60
2) replaced C33 and C29 with jumpers
3) connected one leg of my mundorf 2.7 uF to each signal in; the other leg was soldered to the pot central (same configuration used with my previous Ta2020 board

The test has been performed without any input first, and connected to a source in a second moment

same result for both test; during the test I can heard the thump and screetch from one channel only, the other completely silent

later I discovered the issue on R56

the C47 was 10uF 25V, now I'm installing a 22uF 50V

the C47 was 10uF 25V, now I'm installing a 22uF 50V

this will make the delay before the relay is activated much longer..

at any rate.. regarding the other modifications.. you listed the components but this way only Cristi that has the schematic with the names of the components will be able to help you.. if you want somebody else to try to help you pick a screenshot of the v3b schematic (I guess the input part is the same as v3c) and then highlight the modifications directly on the schematic.. this way would be much simpler to understand what you did..

superrobin ha scritto:ma questo è proprio buffo, perchè ha appena risposto anche a me, ma non mi ha accennato a questi problemi

forse voi avete più confidenza con Christi

Non è afatto buffo,certamente ho più confidenza con Cristi perchè siamo connazionali.Ho voluto darti una mano e gli ho mandato una mail , lui mi ha risposto subbito ed io ho postato la traduzione della sua mail,non ho inventato niente perchè non è mio stile.Per aumentare il gain dell'ampli devi sostituire le resistenze di feedback R 20 e R 24 che sono da 20K con altre resistenze da 33K o al massimo 47K,non andare oltre,le sorgenti hanno di solito in uscita 1Vrms e anche di più.

Florin, non ho mai pensato neanche per un attimo che ti fossi inventato qualcosa

semplicemente non riuscivo a capire la situazione, credevo che Cristi fosse l'adetto al servizio clienti della connex electronic, e tra l'altro ero convinto che operasse dall'europa
ora credo di aver capito che sia un pò un factotum oberato di lavoro, forse anche titolare della società?

Non intendevo offendere nessuno, anche la reazione di Cristi è stata piuttosto dura, evidentemente sono stato frainteso

Cmq grazie per le dritte, ho risolto tutti i problemi, l'ampli funziona, ho aperto un'altro topic

superrobin ha scritto:Florin, non ho mai pensato neanche per un attimo che ti fossi inventato qualcosa

semplicemente non riuscivo a capire la situazione, credevo che Cristi fosse l'adetto al servizio clienti della connex electronic, e tra l'altro ero convinto che operasse dall'europa
ora credo di aver capito che sia un pò un factotum oberato di lavoro, forse anche titolare della società?

Non intendevo offendere nessuno, anche la reazione di Cristi è stata piuttosto dura, evidentemente sono stato frainteso

Cmq grazie per le dritte, ho risolto tutti i problemi, l'ampli funziona, ho aperto un'altro topic

Cristi è il progettista di quello che hai comprato.