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Amp Internals 2

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neonogin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote neonogin Quote  Post ReplyReply Direct Link To This Post Posted: 27 March 2022 at 11:20pm
What boots are you wearing ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 28 March 2022 at 9:24am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monitech Quote  Post ReplyReply Direct Link To This Post Posted: 28 March 2022 at 9:55am
The man had a hand in both ,change the dropper resistors and it will carry on for another 34 years 
phoenix out of the ashes
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 09 April 2022 at 2:19pm
Realistic / Radio shack / Altai / Soundlab MPA100.

Can't recall if this one has been posted before, but anyway, here we are, late 80's, first of the taiwan/chinesey PA amps.

Been sitting in a friends garage the past 25 years. Works fine, even the meters still light up.

Don't think this will do 4kw bridged into 2 ohms though.




Be seeing you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lucasdude Quote  Post ReplyReply Direct Link To This Post Posted: 09 April 2022 at 2:34pm
Originally posted by jbl_man jbl_man wrote:

Realistic / Radio shack / Altai / Soundlab MPA100.

Can't recall if this one has been posted before, but anyway, here we are, late 80's, first of the taiwan/chinesey PA amps.

Been sitting in a friends garage the past 25 years. Works fine, even the meters still light up.

Don't think this will do 4kw bridged into 2 ohms though.






Nice. That's the one I used in the mid 90s to drive a pair of RCF CDs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Static Age Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2022 at 4:21pm
Originally posted by jbl_man jbl_man wrote:

Realistic / Radio shack / Altai / Soundlab MPA100.

Can't recall if this one has been posted before, but anyway, here we are, late 80's, first of the taiwan/chinesey PA amps.

Been sitting in a friends garage the past 25 years. Works fine, even the meters still light up.

Don't think this will do 4kw bridged into 2 ohms though.





If got two of these hooked up to my DAB tuner in my workshop. Quite sturdy & they will put out slightly more than the rated power. I'm sure I heard someone say that they were made by Pyle in the US, no idea if that is true though. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2022 at 4:39pm
Was reading 31.9v per channel at onset of clipping into 8 ohms, which equates to 120w @ 8 ohms.

Says on the back panel "Taiwan",(Altai factory i believe), but these were sold in the USA under the Radio Shack brand, which might explain the US connection.
Be seeing you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 26 April 2022 at 1:25pm
Originally posted by jbl_man jbl_man wrote:

Was reading 31.9v per channel at onset of clipping into 8 ohms, which equates to 120w @ 8 ohms.

Says on the back panel "Taiwan",(Altai factory i believe), but these were sold in the USA under the Radio Shack brand, which might explain the US connection.


By the time Radio Shack embroidered this amplifier it was no longer popular to the masses. I recall Pyramid was toting this amplifier in the 1980's before Radio Shack added this amplifier to it's catalogue.
Amplifiers of such caliber were popular in small Israeli owned electronic stores in the mid to late 1980's. 

Best Regards, 
Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Teunos Quote  Post ReplyReply Direct Link To This Post Posted: 28 June 2022 at 7:31pm
Not sure if this was posted before, Thomann T.amp E4-250.

16kG Class AB amplifier, rated at 4x250W at 8R, 4x400W at 4R.
3x DYP1521 /DYN1521 output devices per channel, no datasheet to be found of these.
2x59V out from the Xformer, 1x 6800uF 100V per half rail, each module (Ch1+2 and Ch3+4) has its own bridge rectifier and set of caps. Both rectifiers are fed from the same Xformer winding though.

The logical way to connect this amp would thus be to have for example Low/High/Low/High and not Low/Low/High/High to spread the power draw.

Tested under load, 1 channel loaded, it does ~52V at 8R and 48.5V at 4R (constant sine wave input @100HZ) which is well over its rated power. I haven't tested all 4 outputs simultaneously.
The clip limiter works as expected and doesn't reduce the output voltage capability, the indicator light comes on at the exact right moment.
Low noise and/or hiss from the outputs with the input potentiometer fully open, barely audible connected to a horn mounted compression driver, ear to horn.


Overall construction looks well though out, the massive downside is the fans, they are loud. 
The fan is some chinesium brand "Tonon TD8025HS" 24VDC brushless fan i can't find much data on. I don't have a tachometer but measured around 303Hz and with 7 blades, it's a 2600rpm fan which draws around 75mA at ~25V, so rather low power fan. With both fans connected and the top cover in place, the amp does around 40ish dB(A) at 1m, very loud.

I just received 2 sunon MF80252V31000UA99 fans with vapo bearing which should be a lot quiter, just need some JST connectors and crimps to connect them.

Unlike stated here: http://https://www.musiker-board.de/threads/the-t-amp-e4-250-seltsame-speakon-belegung.703330/ Thomann seem to have fixed this as the speakons are all wired as expected, CH1&3 have both their channels connected on 1+/- and CH2&4 on 2+/-. Ch2&4 only have 1+/- wired as normal.

The Flir thermal camera spots no significant hotspots to worry about while idle. The section around the bias circuit which is all SMD gets around 50C, and the LM317 linear regs which provide linear supplies in the input circuit are heatshink mounted and get ~55C. Additionally there is a mains input relay near the input connector, which is SanYou SMIH series relay, which has all the appropriate TUV/UL/VDE approvals does get a rather too hot for my liking, it's idling around 55C as well...


Edited by Teunos - 28 June 2022 at 7:46pm
Best regards,
Teun.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Robbo Quote  Post ReplyReply Direct Link To This Post Posted: 28 June 2022 at 8:01pm
Most of the Realistic Hi-Fi amps sold by Tandys back in the day were manufactured or designed in the Hitachi Japanese factory and that rack mount one was probably from there as well as the internals do look very familiar style to me.

Edited by Robbo - 28 June 2022 at 8:03pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote EmPro Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2022 at 9:40am
Originally posted by jbl_man jbl_man wrote:

Actually it was that clean, as Earplug correctly wondered if it was being used as home stereo, it actually came from a home-studio. Apart from a few minor chips and marks to the outside, that is how it arrived.




I think we bought from the same studio LOLLOL:


Edited by EmPro - 01 July 2022 at 9:40am
EmPro Audio
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Post Options Post Options   Thanks (0) Thanks(0)   Quote HonkyJones Quote  Post ReplyReply Direct Link To This Post Posted: 08 July 2022 at 7:14am
Sorry I know this isn't an internal pic, but I saw this in a 2nd hand Electronics market a few years ago in Shanghai...thought it deserves a share.

On the other hand, if anyone has a DICK 'DK1200' internal pic, now is the perfect time to get it out...

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