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The Sequerra Model 1 FM Tuner

The Sequerra Model 1 FM Tuner ; Sequerra Company Inc (ID = 1206833) Radio
 
The Sequerra Model 1 FM Tuner ; Sequerra Company Inc (ID = 1206855) Radio
 
The Sequerra Model 1 FM Tuner ; Sequerra Company Inc (ID = 1207977) Radio
 
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The Sequerra Model 1 FM Tuner ; Sequerra Company Inc (ID = 1213026) Radio The Sequerra Model 1 FM Tuner ; Sequerra Company Inc (ID = 1213027) Radio
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The Sequerra Model 1 FM Tuner ; Sequerra Company Inc (ID = 1213026) Radio
Sequerra Company Inc: The Sequerra Model 1 FM Tuner [Radio] ID = 1213026 933x429
Select picture or schematic to display from thumbnails on the right and click for download.
For model The Sequerra Model 1 FM Tuner, Sequerra Company Inc.; Woodside (NY)
 
Country:  United States of America (USA)
Manufacturer / Brand:  Sequerra Company Inc.; Woodside (NY)
Year: 1974 Category: Broadcast Receiver - or past WW2 Tuner
Valves / Tubes 1: D10-160GH
Semiconductors (the count is only for transistors) 84: E310 2N4959 2N4250 MPS3639 MJE345 2N3440 2N3638 MJE3055 2N5962 2N3644 2N5639 2N5458 2N3569 2N2222 2N5210 2N5784 MC1496 LM301 MC10115 MC10131 SN74H102 SN74196 SN7490 SN7476 SN7404 SN7493 SN74123 µA741 µA723 MV104 5082-7302
Main principle Superhet with RF-stage; ZF/IF 10700 kHz
Tuned circuits 24 FM circuit(s)
Wave bands FM Broadcast Band Only
Details
Power type and voltage Alternating Current supply (AC) / 120; 240 Volt
Loudspeaker - For headphones or amp.
Power out
from Radiomuseum.org Model: The Sequerra Model 1 FM Tuner - Sequerra Company Inc.;
Material Metal case
Shape Book-shelf unit.
Dimensions (WHD) 16 x 5.75 x 12.75 inch / 406 x 146 x 324 mm
Notes

A digital-readout FM tuner with multipurpose oscilloscope and built-in Dolby Noise reduction, in metal case.
Optional: Without "Panoramic"-RF tuning-band display Price: USD 2000,-
Wood-Case: Walnut USD 125,-; Brazilian rosewood USD 150,-
Warranty 5 years parts and labor (scope and incandescent lamps 1 year)
Reviews in Audio Magazine, August 1974
Stereo Review, October 1974
High Fidelity, January 1975
Radio-Electronics, March 1975

Contains also 58 ICs and 4 hp LED displays. Each transistor/IC etc. listed once only.

Price in first year of sale 2'500.00 $
Source of data -- Original prospect or advert
Mentioned in -- Original-techn. papers.

Model page created by Franz Scharner. See "Data change" for further contributors.



All listed radios etc. from Sequerra Company Inc.; Woodside (NY)
Here you find 2 models, 1 with images and 1 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.



 


Forum contributions about this model
Sequerra Company Inc: The Sequerra Model 1 FM Tuner
Threads: 2 | Posts: 12
Hits: 1292     Replies: 0
sequerra: Day Sequerra FM Tuner
Sergio Tomasini
11.May.14
  1

Salve, sono alla ricerca dello schema del sintonizzatore costruito/progettato da Day Sequerra; dovrebbe esse il fratello di di Richard Sequerra che progettò il famoso "Model 1 FM Tuner"

il tuner di Day Sequerra esteticamente è molto simile al FM 1 ma il circuito è molto diverso ; sistemato su di un'unico pcb e non a moduli.

Dovendo procedere alla riparazione, mi sarebbe di estrema utilità avere lo schema .

Qualcuno mi può aiutare?.

Ringrazio anticipatamente.

Sergio Tomasini

 
Hits: 3933     Replies: 10
Sequerra model 1 FM tuner
Enrico Puccini
04.Feb.14
  1

Buonasera,

mi è stato dato da riparare  il sintonizzatore Sequerra Model 1 FM tuner.

L'apparecchio è ora funzionante, per fortuna senza grosse difficoltà vista la complessità circuitale, ad eccezione dell'indicatore a display di sintonia (counter).

Chiedo se qualcuno può avere lo schema elettrico del solo modulo counter non presente in Radiomusuem.

Se necessario posso fare alcune foto ed allegarle.

Saluti a tutti

Enrico Puccini

Bernhard Nagel
05.Feb.14
  2

Buona sera,

lo schema per il contatore di frequenza è ora disponibile per il download, per l'alimentatore troppo. Vorrei anche preparare i documenti ancora mancanti, come matrice di 4 canali, spazzata panoramico, limitatore panoramica e la scheda oscilloscopio. Purtroppo, questi sono solo copie in condizioni mediocri che possiedo, ma schemi migliori per il ricevitore Sequerra Model 1 non sono ottenibili.

Cordiali saluti
Bernhard Nagel


Good evening,
the schematic for the frequency counter is now available for download, for the power supply unit too. I will also prepare the still missing documents, like 4-channel matrix, panoramic sweep, panoramic limiter and the oscilloscope board for upload. Unfortunately, these are only copies in mediocre quality I own, but better schematics for the Sequerra Model 1 are not obtainable.

Enrico Puccini
05.Feb.14
  3

Buonasera, Bernhard

ringrazio infinitamente per aver reso disponibile lo schema del counter per me indispensabile per riportare il sintonizzatore al suo completo funzionamento.

Lo schema contiene inoltre ulteriori informazioni utili per la ricerca del guasto e la risoluzione del problema.

La difficoltà sarà nel recuperare eventuali componenti obsoleti.

Prossimamente inizierò l'indagine.

Ringrazio e saluto

Enrico Puccini

Good evening, Bernhard
 
Thank you very much for making available the essential pattern of the counter for me to return the tuner to its full operation. 
The schema contains minoltre additional information useful for troubleshooting and problem resolution. 
The difficulty will be in recovering eventiuali absoleti components. 
Soon I will start an investigation. 
Thank you and farewell.
 
Enrico Puccini

 

 

Ricardo Cruz
23.Feb.14
  4

Hello Bernhard

I am actually working on a Sequerra FM1 tuner that has problems with the frequency counter.

The tuner works perfectly but the frequency display is fixed on a single value. As the led display works, I am inclined to believe the trouble is in the freq counter itself.

Please let me know if you have any experience with these counters. Allready studying the schematics, but due to it's complexity I welcome all help I can get.

Best regards

Ricardo Cruz

Bernhard Nagel
24.Feb.14
  5

Hello Ricardo,

first, welcome to RMorg's forum!

Indeed, the frequency counter of the Sequerras seems to be unreliable. My tuner have had the same problem, the counter "stucks" to a fixed value 169.6 regardless to which frequency the receiver is tuned:

Fig.1 Freezed freqency display due to a non-working counter

At the first time, this happend only after a "warm-up" period (the Sequerra draws a decent amount of 60 watts!), later on the counter started freezed when powered on.

My first attempt to solve this defect was measuring the time base frequency after checking the correct 5 V power supply. This counter has a 1 MHz crystal (the old big case style with 12 mm pin distance). Using a 1/10 dividing probe and a scope doesn't show up any oscillation. So either the TTL I.C. SN7404 (six inverting buffers) or the crystal should have a defect.

Fig. 2 Counter module, cover removed. 1 MHz crystal at the right side.

Next I tried to cool down the crystal using coolant spray which animates some oscillation for a short time. The crystal needs to be replaced!  This can be done without removing the pcb out of its alumnium box. Be careful when unsoldering the leads from the pcb lugs because they are prone to come apart from the epoxy surface. Best is to cut the wires separately near the old crystal and solder the new one to the remaining wire ends. It depends on the working principle of the new crystal (serial or parallel resonance, crystal cut) wether a series capacitor of about 30 pF will be necessary to be inserted in one lead.

Fig. 3 New quartz crystal aligned to 999.992 kHz

 

Fig.4 hp counter 5345 (1 MΩ input impedance) connected via 1/10 probe to crystal

With my replacement crystal (the only one I had in stock...) this capacitor was inserted for correct frequency reading results. I used first a small variable condenser and aligned to exact 1 MHz. The trimming C was replaced by a small polystyrene film capacitor (33 pF) of the same value.

Fig. 5 Last measurement on the repaired counter unit.

That repair solved the frozen display and brings the counter back to work! Other reasons can also stop the counter from working. If the time base is ok, the incoming signal from the LO buffer amplifier into the counter's preamplifier (MECL) should be traced with an 100 MHz oscilloscope thru the dividing stages. The schematic helps with curve forms/typical patterns to locate the erratic part.

But in most cases the crystal is the delinquent..:) Especially the types with soldered bases seems to be unreliable after a period of some 40 years. The Q of the crystal degrades and if become too low the oscillation will stop.

The better crystals have welded bases and no tin soldered hole at the side. These should last for decades to come...

Bernhard

Enrico Puccini
24.Feb.14
  6
Hello Ricard, 
I recently had a similar problem and thanks to Bernhard has made ​​available to the wiring diagram of the counter I also solved the problem quickly. The circuit diagram shows many interesting notes that "explain" the operation of the circuit. 
In my case, the screen displayed a fixed number and after investigation, with the help of the oscilloscope, a divider by 10 (7490) did not work. After replacing the display perfectly all frequencies received by the tuner. 
I was able to replace the faulty component without removing the board mounted on the module quite complicated. 
 
Greetings
 
Enrico Puccini
Ricardo Cruz
25.Feb.14
  7

Thank you Bernhard

I will test the cristal and post my findings here.

Best

Ricardo

Ricardo Cruz
30.Mar.14
  8

Finally replaced the 1Mhz crystal and the counter now came to life.

Profited to replace alo the stereo pilot light (got it from an automotive surplus retailer)

This tuner is wondefull and sounds like no other I heard before.

Thank you so much for all the schematics and precious comments.

Regards

Ricrdo

PS: Will post some pics later :)

Ricardo Cruz
05.Jun.14
  9

My sequerra counter stopped working again.

Maybe I did not use the correct crystal for the repair.

Please let me know what should be the optimum replacemen part.

Best regards

Ricardo

Ricardo Cruz
23.Jun.14
  10

Finally got it sorted.

Found the ideal quartz oscilator and now it is locked at 1Mhz.

Perfect.

Profited to replace the knob control belt also.

Thank you all for the precious help.

 

Attachments

Ricardo Cruz
15.Sep.14
  11

Hello Bernhard

I am happy to say the counter issues are now completely solved after replacement of the crystal by a compatible model.

Unfortunately I am now having another problem with this wonderfull machine.

The stereo pilot lits when tunning a stereo station but all emissions are received in mono.

The scope in display tuner vector mode does not spread the image so it only shows a vertical pulsating line.

Hope you can guide me searching for a solution.

Best regards

Ricardo

 

 

 
Sequerra Company Inc: The Sequerra Model 1 FM Tuner
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