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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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Old 23rd Sep 2020, 11:55 am   #41
DMcMahon
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Default Re: Brenell Purchases

Quote:
Originally Posted by DMcMahon View Post
Quote:
Originally Posted by brenellic2000 View Post
Alas few second-hand examples have both high and low-speed capstan sleeves. The stud usually carries a bobbin guide to assist in spooling (absent on 10-1/2" models).
On the Series 2 there is a similar looking/sized sleeve fitted on the Supplementary Guide Pillar, which I assumed and was hoping is the small capstan sleeve. What does the bobbin guide look like ?

David
In the attached photo of Mk. V M, does it have the bobbin guide (item with black top) or is it just a different version of the Adjustable Tape Guide (compared to the Mk. V & Mk. V Series 2).

Dave
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Old 23rd Sep 2020, 2:46 pm   #42
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Default Re: Brenell Purchases

In that photo (post 41) the black topped guide is a rotating height adjustable guide. The silver one in your first photo is only height adjustable. The small or large capstan sleeves should not be fitted to the guide pin on the right hand side as tape rubbing against them will cause a flat spot.
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Old 23rd Sep 2020, 4:26 pm   #43
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Default Re: Brenell Purchases

Thank you vidjoman, so "rotating" means that the central bit (collar) of the guide rotates with the moving tape.

My Mk. 5 has the stud in the lid where its spare capstan sleeve was stowed. For the Mk. 5 Series 2 the spare sleeve was fitted to the Supplementary Guide Pin, on the Series 2 where is the spare sleeve supposed to be stowed, do I have a missing stowage stud in my Series 2 lid ?

David
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Old 23rd Sep 2020, 5:42 pm   #44
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Default Re: Brenell Purchases

I think the stud In the lid was only there on early versions. All the decks I owned didn’t have it. When supplied I think it was attached to the pin adjacent to the guide but it should be removed before using the deck. I think that’s why they are often missing. You only need the small one for 1.75 ips.
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Old 24th Sep 2020, 8:23 am   #45
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Default Re: Brenell Purchases

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Originally Posted by DMcMahon View Post

Cleaned the sticky mess off the 4 motor "Dubilier SFK24R" CR suppressor transorbs (0.02uF + 220 ohms), no sign that it leaked out of the suppressors.
Correction in bold to above from my Post # 40. (0.01uF + 220 ohms)
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Old 6th Oct 2020, 4:28 pm   #46
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Default Re: Brenell Purchases

Many days back now connected the Series 2 amplifier module to the Series 2 power supply and powered up.

Only valve in the amplifier was the EM 87 magic eye (only powered in Record). HT voltage again was very high around +450 volts. Fitted an EF 86 valve (only spare valve immediately to hand) but still no change to the high HT voltage.

Had to reduce the mains voltage supply to the unit down to around 160 volts by Variac to get the HT output down to around 290 volts, a more comfortable/typical level.

Once I find some donor valves for the other missing valves will fit them and see if any change to the HT voltage. Am hoping that the HT voltage might come down when the output pentode is fitted. I know from some of the old Grundigs that with the output pentode not fitted the HT voltage can be around 100 volts higher than normal, not sure what mechanism causes this, do not think it is current limiting when all valves are fitted.

Will be interesting to see what the Mk. 5 HT voltage is like in comparison.

In the meantime first will check out the grid coupling capacitors.
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Old 7th Oct 2020, 7:56 am   #47
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Default Re: Brenell Purchases

The output valve takes most of the current. None of the signal valves will significantly load the PSU.
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Old 8th Oct 2020, 10:24 pm   #48
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Default Re: Brenell Purchases

Checked out the 3 grid coupling capacitors on the Mk. 5 Series 2, two were fairly leaky so renewed, the third (good one) was a 22,000pF (0.022uF) yellow mustard type.

The 2 bad ones (0.1uF) were Hunts, one a black AD51 and the other a nice looking red G51. Also replaced another red G51 (0.1uF) the coupling capacitor to the external amplifier output socket, this one was very leaky (passing a lot of DC volts).

There are another two Hunts 0.1uF capacitors (one black AD51 and one red G51) but they do not see DC volts, but I will replace them later.

On the Series 2 schematic none of the resistors and capacitors are identified component number wise. Looking at the Series 5 schematic for comparison (which does provide component identification numbers) could see that even though very similar, there are quite a few component value differences and some circuitry connection differences, compared to the Series 2.

Borrowed an ECC 83 (from Grundig TK 120) and an EL 84 (from Simon Minstrelle) so that could power up with all valves fitted. With the Variac set to 240 volts mains output, the DC +HT supply now reduces down from its previous 450 volts to around 330 volts (at 40mA drain).

Schematic shows 285 volts for the +HT, so the HT is still somewhat high, to get HT down to around 285 volts, have to reduce the output of the Variac down to around 205 volts.

With amplifier switched to Playback, there is a horrible loud fast ticking sound from the loudspeaker as soon as the volume control is adjusted away from its minimum setting. With amplifier switched to Record or Amplifier there is no sound from the speaker.

There is also a faint fast ticking sound heard from the power supply, even at zero volume setting, HT output at this time is still mains ripple free.

Had a quick look at the electronics with scope, and when the volume control is moved away from zero, there is a very clean regular spikey pulsed signal all over the electronics at 60mS (16Hz). With scope connected to the input of the pre-amp EF 86 (Control Grid pin 9) there is a constant 32 Hz (30mS) pulsed signal even at zero volume setting, the scope connection is obviously modifying the pulsed signal because the sound from the loudspeaker changes.

Currently do not have the tape deck connected, so the PB head is not connected into the EF 86 (when switched to Playback), so wondering if the EF 86 is breaking into oscillation due to no head connection (seems odd though).

Tomorrow will connect the tape deck and see what happens.
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Last edited by DMcMahon; 8th Oct 2020 at 10:34 pm. Reason: Typo correction
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Old 9th Oct 2020, 8:09 am   #49
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Default Re: Brenell Purchases

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Looking at the Series 5 schematic for comparison.
Correction to above (from previous Post) Looking at the Mk. 5 schematic for comparison.
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Old 9th Oct 2020, 9:22 pm   #50
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Default Re: Brenell Purchases

Before connecting the tape deck decided to do some more checks to try and establish where the horrible loud ticking noise is originating from.

Found that the faint ticking sound (with volume turned right down) that I previously thought was coming from the power supply, was in fact coming from the speaker (speaker siting right next to the power supply).

Scope measured the PB/Record head socket input and saw the same pulsed noise signal as seen at the EF 86 control grid.

With the EF 86 removed and also with the EF 86 back in with its grid coupling capacitor to next valve (ECC 83) disconnected, the noise stops, supporting the fact that the noise signal is pre ECC 83.

Tried another EF 86 and also fitted a screening can to it but no change. Closely checked all the components/wiring around the EF 86. A Hunts 4uF/150 volt electrolytic de-coupling the EF 86 screen grid, only measured 0.2uF with high ESR (140 Ohms). Replaced it with a NOS 4.7uF/100 volt but no change.

The Series 2 schematic shows the capacitor to be 8uF but the 4uF looked original, the same capacitor shown in the Mk. 5 schematic is only a 0.5uF

Found two 27k resistors in the HT chain measure around 35k so 30% high, will replace those later.

Disconnecting the 0.05uF capacitor that connects the PB/Record head amplifier socket through (via switch contacts) to the control grid of the EF 86, stops the noise, supporting theory that the unterminated input (no head connection) is the root cause of the noise, causing the EF 86 to effectively self oscillate.

Connected tape deck and no more horrible noise. With volume wound up there is quite a bit of audible mains hum at the speaker, will check that out more, once tape deck operation checked out and tape playback working.
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Old 10th Oct 2020, 8:08 pm   #51
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Default Re: Brenell Purchases

Forgot to mention that during previous investigation into the ticking noise that grounding the input of the PB/Record head socket at the amplifier (i.e. tying down the floating input of the 0.05uF EF 86 Grid coupling capacitor) stops the noise/valve from oscillating.

Checked some more of the main components in the amplifier. Replaced the two 50uF/12V electrolytics for the 2 cathodes of the ECC 83, used NOS 47uF/16V. One of the originals had high ESR and the other one was totally open circuit. Also replaced 4.7kOhm resistor that was in parallel with the O/C capacitor, it was reading around 8k

Replaced (with new 0.1uF/600V Poly) the 2 remaining 0.1uF Hunts capacitors, one was a little leaky, the other a lot. One was on the 1 7/8 ips equalisation circuit , the other on the EM 87 Magic Eye Control grid.

At least 4 resistors I will replace later when correct values obtained, as they were around at least 30% higher that their stated values (they were 10% silver banded tolerance).
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Last edited by DMcMahon; 10th Oct 2020 at 8:17 pm.
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Old 15th Oct 2020, 7:48 pm   #52
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Default Re: Brenell Purchases

Replaced a bunch of resistors on the Series 2 amplifier which had gone way above their max tolerance values.

2 x 27k on HT dropper chain.
47k on ECC83 V2A anode HT line.
82k on EL94 V3 Control grid.
100k on ECC83 V2B anode.
100k on EM87 V5 pre-set VR1.
100k on EM87 V5 anode, while replacing this noticed that there was a 33k on pin 6 (Target) connecting up to top end of the 100k to pick up the switched (in Record) HT supply, but the schematic shows no 33k just a direct connection.
220k on Radio input.
220k on volume control input.
470k on input to EL84 V3 82k Control grid resistor.
1M on mic input.
10M on EM87 V5 Control grid.
10M on EF86 V1 Control grid.

Cleaned out the case, even though it looked fairly clean, amazing how much dirt (plus a few small live spiders) came out.

Will fit all parts back in case and try out the tape deck operation.
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Old 16th Oct 2020, 5:24 pm   #53
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Default Re: Brenell Purchases

Fitted the power supply and amplifier back into the case (no tape deck) and powered up

Previously had been testing most of the time at 200 volts mains voltage from Variac unit because at 240 volts mains the DC voltage goes too high for comfort.

So was very surprised to see the HT voltage (running at 200 volts mains) was now 30 to 40 volts lower, surprised because nothing electrically has changed.

Increased the mains voltage up to 240 volts and HT voltage then increased to around 270 volts, which is lower than it should be. While thinking about it, smelt a burning smell so switched off. Looks like the 470 ohm 1 watt resistor that connect the 50uF reservoir capacitor to first smoothing/filter 50uF capacitor has got a bit cooked, although still measures reasonably OK, so assume must be drawing too much current. Previously has run OK for short periods at 240 volts so do not know what has changed.

I know from previous tests that the load current is between 30 to 40mA will recheck it and try and work out what is going on.
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Old 18th Oct 2020, 10:59 am   #54
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Default Re: Brenell Purchases

Hello Dad bought a Gold one with a white head cover in 1959, interesting that it has a meter and not a EM87 valve for level . The original mike has gone missing unfortunently.
Cheers
Geoff.
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Old 18th Oct 2020, 11:48 am   #55
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Default Re: Brenell Purchases

I think that a microphone was an optional extra - and a choice on many that were current at that time. All the Brenell models I owned from new didn't come with a supplied mic. Maybe the cheaper,3 Star more domestic model, was supplied with a mic so as to be ready for recording.
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Old 18th Oct 2020, 4:23 pm   #56
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Default Re: Brenell Purchases

As I understand from reading the Brenell book, when the Mk. 5 first came out it had the EM81 Magic Eye recording level valve. Then after the introduction of the MK. 5M which had the moving coil meter, the same meter circuitry became an option on the Mk. 5.

Then subsequently when the Mk. 5 Series 2 and Series 3 came out they by default had the EM87 Magic Eye valve with the option of having the moving coil meter circuitry.

David
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Old 20th Oct 2020, 6:44 am   #57
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Default Re: Brenell Purchases

Microphones were originally 'extra' from the basic ACOS models to the more advanced Lustraphone range, followed by Reslo or Grampian, but whether supplied by Brenell or their dealers is another matter.

Brenells were very accommodating to individual needs (customers often visited the works to chat) and offered from an early date optional extras that soon became standard: digital counters, record level meters... stereo monitor amp and speakers on the STB... and all manner of specs of the Type 19.
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Old 20th Oct 2020, 10:59 pm   #58
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Default Re: Brenell Purchases

Started investigating Post 53.

Visually found another resistor that looked somewhat cooked (sure it looked OK before) a large 10kOhm (1/4 watt according to parts list) connected to the output side of the 470 Ohm and feeding HT supply down to the Screen grid of the EL 84 output pentode. Even though the 10k looks cooked it measures OK.

Started rechecking all the previous component replacements in case I had done something incorrect, but nothing untoward found so far. After the previous batch of component replacements, I had thoroughly checked all the voltages and everything basically measured OK, it was only after putting the power supply and amplifier back into the case that the problem at Post 53 occurred.
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Old 21st Oct 2020, 1:14 pm   #59
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Originally Posted by DMcMahon View Post
Started investigating Post 53.

Visually found another resistor that looked somewhat cooked (sure it looked OK before) a large 10kOhm (1/4 watt according to parts list) connected to the output side of the 470 Ohm and feeding HT supply down to the Screen grid of the EL 84 output pentode. Even though the 10k looks cooked it measures OK.

Started rechecking all the previous component replacements in case I had done something incorrect, but nothing untoward found so far. After the previous batch of component replacements, I had thoroughly checked all the voltages and everything basically measured OK, it was only after putting the power supply and amplifier back into the case that the problem at Post 53 occurred.
Is the load current still at 30-40 mA as you'd previously established pre post 53?

Mike

Last edited by Boulevardier; 21st Oct 2020 at 1:22 pm.
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Old 21st Oct 2020, 6:31 pm   #60
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Default Re: Brenell Purchases

Not yet had a chance to check, had a very interesting day at Amberley Museum.

David
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