14th Aug 2017, 10:42 am | #21 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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Thank you Kane |
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14th Aug 2017, 1:42 pm | #22 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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First - -181.1 Millivolt Second - -30.6 Volts Third - -163.3 Millivolts Fourth - -30.7 Volts I did try to convert from Millivolts to volts but it's just showing as not even 1 volt coming from them Thank you Kane |
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14th Aug 2017, 1:50 pm | #23 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
You're missing the 15V supply then.
Check the voltage on the fuses as described earlier.
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14th Aug 2017, 2:00 pm | #24 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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Thank you Kane |
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14th Aug 2017, 3:09 pm | #25 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
Can you clarify that please. Was one lead connected to the chassis? If you're using a DMM it doesn't matter which.
You should be able to take four readings in all, two fuses with two ends.
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14th Aug 2017, 4:00 pm | #26 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
In anticipation of the direction this thread is likely to take, I've attached an extract from the service manual.
There are plenty of voltages to be checked here. To avoid red herrings check that with your speakers connected to the adaptors, but not the the amp, you measure a low resistance (not a short-circuit) across the DIN pins of the adaptor
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14th Aug 2017, 5:10 pm | #27 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
OK so I know what is going on. There are two diodes which are NKT279, they look like transistors, they develop tin whiskers.
Look at the picture which I've copied from your picture. You will see two blocks of small heatsinks (arrowed) Remove the pillar and then remove only the top two transistors. Remove them from their heatsink (the copper part) Wrap each transistor in one thin layer of Sellotape then refit the heatsink and refit both to the other heatsink and secure with the pillar. Repeat for the other block. If the picture hasn't come out well, I'll take more later and post them here. |
14th Aug 2017, 9:30 pm | #28 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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Thank you Kane |
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14th Aug 2017, 9:34 pm | #29 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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Also thank you for the extract I will look through them all ASAP Thank you Kane |
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14th Aug 2017, 9:36 pm | #30 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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Thank you Kane |
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14th Aug 2017, 9:42 pm | #31 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
No same side, you do the same for both sets of transistors
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14th Aug 2017, 11:19 pm | #32 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
I'll leave this one to Michael who obviously knows these amps well.
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15th Aug 2017, 12:42 pm | #33 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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Do you mean just switch them around once I've sellotaped them, then the same with the other two? Sorry I'm about to do it that's all and got confused by the wording. Thank you Kane |
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15th Aug 2017, 12:53 pm | #34 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
No. Do exactly as described. There's no need to disconnect the legs, but be very careful not to break them off. Open up the heatsink very slightly and carefully remove each top transistor and wrap the tape as described and carefully re-insert them in the copper heatsink. It sounds like a bodge but will probably last for another fifty years - done it quite a few times on these.
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15th Aug 2017, 1:07 pm | #35 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
To explain further, these parts are prone to growing very fine threads of metal ('tin whiskers') between the case and the functional bits inside. In this design, the cases are clipped inside metal heatsinks, which are connected to earth. Fitting a layer of sellotape around the case stops it being earthed through the heatsink, and the tin whiskers then have no effect.
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15th Aug 2017, 1:08 pm | #36 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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Thank you Kane |
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15th Aug 2017, 1:11 pm | #37 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
Yes.
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15th Aug 2017, 2:08 pm | #38 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
Attached is the photo of them both once I'd sellotaped them, is that alright?
Now I just try and test the system to see if the speakers work? Thank you Kane |
15th Aug 2017, 2:53 pm | #39 |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
That looks about right. Put them back in the heatsinks though.
If you measure the voltages around the output transistors again, they should have changed. |
15th Aug 2017, 2:59 pm | #40 | |
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Re: Dynatron SRX25 Radiogram with Garrard 40B, Sound Issue
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I honestly wouldn't even mind if it was white noise coming out. Thank you Kane |
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