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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc. |
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Thread Tools |
9th Apr 2021, 3:39 pm | #21 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Has to be R6 and / or the trip cap c12. Of course R6 wil have to be stuck under the left drive pulley
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9th Apr 2021, 4:29 pm | #22 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Well I checked R6. Was about 330k. So replaced it anyway. Did not fix the problem.
Maybe the head is worn ? But why will a tape from another unit play loud ? Next to check the trim pot. C12 |
9th Apr 2021, 4:29 pm | #23 |
Heptode
Join Date: Jan 2011
Location: Croydon, London, UK.
Posts: 767
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Re: EL3516 no sound
On record, the signal is applied to the head via contacts 9/10, 15/16 and R29. If R29 has risen in value you would have the symptoms you describe (good signal levels at the magic eye but very low level record.
A less likely possibility is that C14, the bias trimmer capacitor has gone short circuit. I would expect that to result in a muffled recording, which doesn't seem to be the case here. Paula |
9th Apr 2021, 5:09 pm | #24 |
Heptode
Join Date: Jan 2011
Location: Croydon, London, UK.
Posts: 767
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Re: EL3516 no sound
Just noticed that R29 on the circuit I was looking at is the same as R6 on the second circuit that was posted. That has been suggested by others already and it's the one you have just checked.
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9th Apr 2021, 5:10 pm | #25 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Paula,
I can’t find R29. The schematics for this are at the start of my thread. Have attached here, shown with the unit in record mode. Can’t find r29 I have checked or replaced the items circled in red. Totally out of ideas without my oscilloscope to check the signal at the head. It does erase without any input. |
9th Apr 2021, 5:14 pm | #26 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Is it possible to have a worn head that will record weak undistorted audio but play loudly pre recorded tapes ?
Never had this kind of prob with my Grundig’s. As long as the oscillator is working and head coils are good I get all functions. |
9th Apr 2021, 5:29 pm | #27 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Well I checked the whole path shown in blue and including the contacts. Matches very close. The head is around 800 ohms.
Has to be a worn head that can play but can’t record. Until I get an oscilloscope I can’t do more. Ahhh. |
9th Apr 2021, 5:31 pm | #28 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
The side inputs R and L Don't seem to work at all. Maybe they need more drive?
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9th Apr 2021, 6:05 pm | #29 | |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
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Re: EL3516 no sound
Quote:
R29 is shown in your first attachment for the EL3516/42, equivalent to R6 in the second attachment, i.e. the schematics in the 2 attachments at Post # 1 are similar but not identical, at least there are component designation differences. David |
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9th Apr 2021, 6:07 pm | #30 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Tks. Mine is definitely the 2nd schematic. It’s a very early one. Has R6.
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9th Apr 2021, 6:08 pm | #31 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
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Re: EL3516 no sound
Are you happy that the tape is not back to front, i.e. you are not recording on the wrong side of the tape ?
David |
10th Apr 2021, 2:10 am | #32 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
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Re: EL3516 no sound
I am using the same tape on my Lexus TK1 Grundig as my recording unit. Which I then play back and try recording on the Philips. 100% sure the tape is not reversed. Tried another tape as well.
I thought it was the inputs on the left as they don’t seem to work or my signal is too low. However given the magic eye is working I assume it’s ok up to that point of the circuit. |
10th Apr 2021, 11:24 pm | #33 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Checked path in blue with a multimeter. All ok from the two red lines
Components with circles were checked or replaced |
11th Apr 2021, 8:51 am | #34 | |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
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Re: EL3516 no sound
Quote:
The tape should contact the combined Play/Record head the same in Playback and Record modes, but make sure the tape is making good physical contact, is there any pressure pad arm to hold the tape against the heads ? Ideally really need to scope the record signal (when scope available) to make sure that actually getting a good record bias signal (amplitude and frequency) arriving at the head in record mode and that the audio signal is superimposed/modulated onto the bias signal (can be very difficult to see the audio signal on the record bias due to the huge difference in their amplitudes). I don't suppose you have a valve voltmeter/FET multimeter etc, i.e. a meter capable of measuring the high frequency record bias signal ? David |
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11th Apr 2021, 10:50 am | #35 |
Octode
Join Date: Mar 2006
Location: Lund, Sweden
Posts: 1,631
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Re: EL3516 no sound
In the video I noticed that the magic eye appears to be an EM80; it should be an EM81 in this machine (the EM80 was primarily intended for radios). The two have different beam patterns (the EM81 has two bright segments which come together as the signal level increases and eventually overlap (indicating tape overload), whereas the EM80 has essentially a single bright segment which widens as the signal is increased (eventually meeting up two smaller segments one on each side)) but I don't know if there's any difference in sensitivity though which could at least partly account for the incorrect recording level.
Otherwise I thought the recording sounded fine in the video, which indicates that the record bias level is reasonably correct. There was a lot of scratch noise when the playback volume was adjusted though, which to me indicates that there's a lot of DC on the pot, indicating a leaky coupling capacitor in the preceding valve stage. In this situation, I'd go over the valve grids and see that there is not undue DC on any of them as that could partly be the cause for low volume. |
12th Apr 2021, 12:21 pm | #36 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
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Re: EL3516 no sound
The top RCA input connector you are using to record, has it got any identification/icon, i.e. could it be the microphone input, if it is and you are feeding in a line level signal to record (with an unattenuated cable) then the Recorded playback would be very loud and most likely distorted.
Are the side connectors you reference the 3 pins (inline) type as shown in the first schematic ? cannot easily see them in your second schematic. David |
12th Apr 2021, 12:25 pm | #37 | |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
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Re: EL3516 no sound
Quote:
David Last edited by Cobaltblue; 12th Apr 2021 at 12:40 pm. Reason: Fixed quote |
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12th Apr 2021, 12:27 pm | #38 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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Re: EL3516 no sound
Radio/Pickup.
Lawrence. Last edited by ms660; 12th Apr 2021 at 12:39 pm. Reason: word change |
12th Apr 2021, 3:03 pm | #39 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Ok. I got a Cro from work and there appears way too much bias drive to the head
Voltage across R21 is 776mV. Should be 4 according to the schematic C12 head end is 246v However when I connect my volt meter in parallel with the cro from C12 head end to ground the voltage drops to 140v from 246v C12 other end is 508v ? See photos please. Very strange Last edited by Phantomrose1999; 12th Apr 2021 at 3:13 pm. |
12th Apr 2021, 3:31 pm | #40 |
Hexode
Join Date: Mar 2008
Location: Melbourne, Victoria, Australia
Posts: 289
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Re: EL3516 no sound
Well I connected the cro directly to the play head and a getting 262v !
Immediately checked the 10:1 probe setting in the cro and it’s correct Surely there can’t be this much voltage there ? Usually around 24v See photos. |