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Messages - Vitrolin

Pages: 1 [2] 3 4 5
16
Tubes and Hybrids / Re: AC30 VR doesn't produce sound.
« on: April 27, 2016, 12:51:37 PM »
after posting i reread your question...

capacitors shouldn't get hot, my guess is that its shorted.
wich capacitor is getting hot?
with your amp turned off, take your meter and measure the resistance or conductivity of the capacitor.

i posted a schematic

17
Tubes and Hybrids / Re: AC30 VR doesn't produce sound.
« on: April 27, 2016, 12:42:06 PM »
hey

check the supply voltages, both the regulated (used for preamp) and the unregulated (used for poweramp).
unregulated should be around +/-26V measured on diode bridge og C13/C22
and regulated +/-15V measured on C19/C28

18
Amplifier Discussion / Re: Amperes required by LM1875 Guitar Power Amp
« on: April 25, 2016, 03:55:18 PM »
PS: Since the Philippines' electrical system doesn't have grounding (true earth) after entering residential meters (i heard that one of our two prong outlets is actually grounded but not sure which one), if I am to just let my circuit's common float, of course common to chassis connection is a BIG NO. Aside from that, do you have any suggested modifications, additions or other reminders for a floating ground circuit? I still have a plan to add true grounding in the future if it's safer.

neutral (N), most likely blue cord, should be equal to earth, if there isn't a 3 prong outlet, leave it floating don't ever connect chassis to another cord than ground, someone WILL get electrocuted if phase and neutral gets switched around in a way that phase is connected to chassis (and guitar player).

earth isn't connected through the meter but most probably to the frame where meter and fuse boxes are mounted. or a in houses a ground spear hammered in the ground.

a ground connection is safer it removes the accumulated voltage difference between appliances,  so no more minor electric shocks around the house,

19
maybe is just me but to smack something sounds hard, guess i mixed with punch...
I usually go for something like a light pad or lifting the amp a few cm at one end and let it fall... and somethines with the lights out, or low you can see the spark at the loose connection.

20
i like the fact that you chose smack the PCB in your beloved very rare 50 year old amplifier, but i know the feeling when you start to think a "Phillips adjustment" is needed.

by the way transistors do not need to warm up, there is a great deal of work in removing the heat from the transistors, ideally they should not produce heat, but they do.

21
Tubes and Hybrids / Re: Ibanez TSA30 Mains transformer
« on: March 15, 2016, 04:47:48 PM »
yes that is very much what i was thinking, the given voltages are what is finally needed, execept that 13V, used for 10V.
i havent seen the the amp myself, maybe it isn't connected as shown in the schematic, maybe the heaters are connectet to the un regulated dc, not after 7810, bu why aren't they supplied with the power tube and phase inverter heaters??
my friend called me for help, figuring out the transformer, he says he wants to fixit himself, hes a trained technician so he will be ok i think.

22
Tubes and Hybrids / Re: Ibanez TSA30 Mains transformer
« on: March 14, 2016, 07:14:05 PM »
by the way i guess that the voltages are noted after rectification
400*1,4=560Vdc wouldn't it be to high for only 30W?

and the bias is only half-wave rectified
47*0,7=33vdc

23
Tubes and Hybrids / Re: Ibanez TSA30 Mains transformer
« on: March 14, 2016, 06:40:34 PM »
i was convinced that i did, but something didn't go well

24
Preamps and Effects / Re: DBX 160X
« on: March 14, 2016, 06:03:20 PM »
i just realized that LF351 is rated max +/-18V so its very good that you don't have +/-24V :duh
ofcourse there is two voltage dividers R115-116 and R120-122 so maybe +/-12V would be ok
the voltage divider is affected by the push-pull transistors (no designators) and the components around them.
i would start by mesuring voltages at the top and bottom of the two dividers, if supply i good, most go to the transistor stage..

25
Preamps and Effects / Re: DBX 160X
« on: March 14, 2016, 05:44:41 PM »
well it isn't powered ok + and - should be sort of the same, the both come from the unregulated supply
If you look at the connector J112 that shown as to be connected to P101 the positive 24V (Pin 6) is supply to U103 so around +/- 24V is good +17 and -12 very bad... if i have read the schem correctly there is a lot of long thin parallel lines..

26
Tubes and Hybrids / Re: Ibanez TSA30 Mains transformer
« on: March 14, 2016, 05:22:24 PM »
last night after posting i got a great idea and i wrote ibanez they replyed first thing in the morning with a schematic

so sometimes its so easy to get an answer, just direct your question to the right place xP

27
Tubes and Hybrids / Ibanez TSA30 Mains transformer
« on: March 13, 2016, 06:37:07 PM »
A friend has Ibanez TSA30, he was playing loud for a long time then it died..

He measured the primary side and seems as the internal thermal fuse has blown, so he asked me if i knew what the mains transformer for his Ibanez TSA30 was.
i tried google and only found this schematic http://gravinatubeamps.com/2014/08/02/ibanez-tsa-30-u-schematic/ that lack exactly what i am looking for.
so does anyone have a full schematic, have TSA30 you can open to take some measurements, or by some other reason know what the transformers secondary voltages are, the would bring a lot of joy.

28
Amplifier Discussion / Re: Roland JC120 too bright
« on: March 01, 2016, 04:40:11 PM »
congrtulations

C4 and C8 negative feedback so increasing them would give less high frequency since it gets cancelled out.
about C16 you could play around with tonestack calculator to get a sort of idea where to go..
in the schematic it looks like the treble pot is linear maybe a logarithmic pot would give you a better feel.

29
Amplifier Discussion / Re: TDA7294 Power Amp with Fender Clean Sound Preamp
« on: February 26, 2016, 04:36:20 PM »
i agree with fahey old power am with a guitar pre amp wiorks quite good.
for a time used a peavey cs-800... i was LOUD, and unlike many other guitarists i had no problem hearing myself if i turned up the volume, eventually the fan broke and the output stage overheated, not by my playing, when it was used for PA at a party.
its now waiting for some new output transistors.

30
Tubes and Hybrids / Re: Performer/Roc-pro transformer
« on: February 23, 2016, 06:44:10 PM »
R113 doesn't burn up because of the heat sinks, it burns because Q13 is conducting too hard, and is likely defective.  Especially if R115 is not also burning.

yes, my point was that the heat sink didnt do it for output transistors so at least on died, in this case Q13 shortet.


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